CRISPR: Difference between revisions
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{{short description|Family of DNA sequence found in prokaryotic organisms}} |
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[[File:GRNA-Cas9.png|thumb|306x306px|CRISPR/Cas9]] |
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{{cs1 config|name-list-style=vanc|display-authors=6}} |
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[[File:Crispr.png|thumb|450px|right|Diagram of the CRISPR prokaryotic antiviral defense mechanism.<ref name="pmid20056882" />]] |
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{{About|the prokaryotic antiviral system|the use in editing genes|CRISPR gene editing}} |
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'''CRISPR''' ({{IPAc-en|ˈ|k|r|ɪ|s|p|ər}}) is a family of [[DNA]] sequences in bacteria and archaea.<ref name="pmid25574773" /> The sequences contain snippets of DNA from viruses that have attacked the [[prokaryote]]. These snippets are used by the prokaryote to detect and destroy DNA from similar viruses during subsequent attacks. These sequences play a key role in a prokaryotic defense system,<ref name="pmid25574773">{{cite journal | vauthors = Barrangou R | title = The roles of CRISPR-Cas systems in adaptive immunity and beyond | journal = Current Opinion in Immunology | volume = 32 | issue = | pages = 36–41 | year = 2015 | pmid = 25574773 | doi = 10.1016/j.coi.2014.12.008 }}</ref> and form the basis of a technology known as '''CRISPR/Cas9''' that effectively and specifically changes genes within organisms.<ref name="pmid24651067">{{cite journal | vauthors = Zhang F, Wen Y, Guo X | title = CRISPR/Cas9 for genome editing: progress, implications and challenges | journal = Human Molecular Genetics | volume = 23 | issue = R1 | pages = R40–6 | year = 2014 | pmid = 24651067 | doi = 10.1093/hmg/ddu125 }}</ref> |
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CRISPR is an abbreviation of '''C'''lustered '''R'''egularly '''I'''nterspaced '''S'''hort '''P'''alindromic '''R'''epeats.<ref name="sawyer2013">{{cite web | url = http://www.nature.com/scitable/blog/bio2.0/editing_genomes_with_the_bacterial | title = Editing Genomes with the Bacterial Immune System | last = Sawyer | first = Eric | name-list-format = vanc | date = 9 February 2013 | website = Scitable | doi = | pmid = | access-date = 6 April 2015 | publisher = Nature Publishing Group}}</ref> The name was minted at a time when the origin and use of the interspacing subsequences were not known. At that time the CRISPRs were described as segments of [[prokaryotic]] [[DNA]] containing short, repetitive base sequences. In a [[palindromic sequence|palindromic]] repeat, the sequence of [[nucleotide]]s is the same in both directions. Each repetition is followed by short segments of [[spacer DNA]] from previous exposures to foreign DNA (e.g., a [[phage|virus]] or [[plasmid]]).<ref name="pmid20125085">{{cite journal | vauthors = Marraffini LA, Sontheimer EJ | title = CRISPR interference: RNA-directed adaptive immunity in bacteria and archaea | journal = Nature Reviews Genetics | volume = 11 | issue = 3 | pages = 181–90 | date = March 2010 | pmid = 20125085 | pmc = 2928866 | doi = 10.1038/nrg2749 }}</ref><ref name="Mojica_2000" /> Small clusters of ''cas'' (CRISPR-associated system) genes are located next to CRISPR sequences. |
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The CRISPR/Cas system is a [[prokaryotic]] [[immune system]] that confers resistance to foreign genetic elements such as those present within plasmids and [[phage]]s<ref>{{cite journal | vauthors = Redman M, King A, Watson C, King D | title = What is CRISPR/Cas9? | journal = Archives of Disease in Childhood. Education and Practice Edition | volume = 101 | issue = 4 | pages = 213–5 | date = August 2016 | pmid = 27059283 | pmc = 4975809 | doi = 10.1136/archdischild-2016-310459 }}</ref><ref name="pmid17379808">{{cite journal | vauthors = Barrangou R, Fremaux C, Deveau H, Richards M, Boyaval P, Moineau S, Romero DA, Horvath P | display-authors = 6 | title = CRISPR provides acquired resistance against viruses in prokaryotes | journal = Science | volume = 315 | issue = 5819 | pages = 1709–12 | date = March 2007 | pmid = 17379808 | pmc = | doi = 10.1126/science.1138140 | bibcode = 2007Sci...315.1709B }} {{Registration required}}</ref><ref name="pmid19095942">{{cite journal | vauthors = Marraffini LA, Sontheimer EJ | title = CRISPR interference limits horizontal gene transfer in staphylococci by targeting DNA | journal = Science | volume = 322 | issue = 5909 | pages = 1843–5 | date = December 2008 | pmid = 19095942 | pmc = 2695655 | doi = 10.1126/science.1165771 | bibcode = 2008Sci...322.1843M }}</ref> that provides a form of [[acquired immunity]]. RNA harboring the spacer sequence helps Cas (CRISPR-associated) proteins recognize and cut exogenous DNA. Other RNA-guided Cas proteins cut foreign RNA.<ref name=Mohanraju2016>{{cite journal |vauthors = Mohanraju P, Makarova KS, Zetsche B, Zhang F, Koonin EV, van der Oost J |title=Diverse evolutionary roots and mechanistic variations of the CRISPR-Cas systems |journal=Science |volume=353 |issue=6299 |pages=aad5147 |year=2016 |pmid=27493190 |doi=10.1126/science.aad5147 }}</ref> CRISPRs are found in approximately 40% of sequenced [[bacterial genome]]s and 90% of sequenced [[archaea]].<ref name="pmid17521438">{{cite journal | vauthors = Grissa I, Vergnaud G, Pourcel C | title = The CRISPRdb database and tools to display CRISPRs and to generate dictionaries of spacers and repeats | journal = BMC Bioinformatics | volume = 8 | pages = 172 | date = May 2007 | pmid = 17521438 | pmc = 1892036 | doi = 10.1186/1471-2105-8-172 }}</ref><ref group="note">71/79 Archaea, 463/1008 Bacteria [http://crispr.u-psud.fr/crispr/CRISPRdatabase.php CRISPRdb], Date: 19.6.2010 {{webarchive |url=https://web.archive.org/web/20150516061838/http://crispr.u-psud.fr/crispr/CRISPRdatabase.php |date=May 16, 2015 }}</ref> |
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==Use for gene editing== |
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A simple version of the CRISPR/Cas system, CRISPR/Cas9, has been modified to edit genomes. By delivering the [[Cas9]] nuclease complexed with a synthetic [[guide RNA]] (gRNA) into a cell, the cell's [[genome]] can be cut at a desired location, allowing existing genes to be removed and/or new ones added.<ref name="nature99" /><ref name="vb99" /><ref name="pmid26121415">{{cite journal | vauthors = Hendel A, Bak RO, Clark JT, Kennedy AB, Ryan DE, Roy S, Steinfeld I, Lunstad BD, Kaiser RJ, Wilkens AB, Bacchetta R, Tsalenko A, Dellinger D, Bruhn L, Porteus MH | title = Chemically modified guide RNAs enhance CRISPR-Cas genome editing in human primary cells | journal = Nature Biotechnology | volume = 33 | issue = 9 | pages = 985–9 | date = September 2015 | pmid = 26121415 | doi = 10.1038/nbt.3290 | pmc=4729442}}</ref> The Cas9-gRNA complex corresponds with the CAS III CRISPR-RNA complex in the above diagram. |
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CRISPR/Cas genome editing techniques have many potential applications, including medicine and crop seed enhancement. The use of CRISPR/Cas9-gRNA complex for [[genome editing]]<ref>{{cite journal | vauthors = Ledford H | title = CRISPR: gene editing is just the beginning | journal = Nature | volume = 531 | issue = 7593 | pages = 156–9 | date = March 2016 | pmid = 26961639 | doi = 10.1038/531156a }}</ref><ref>{{Cite web|url=https://www.wired.com/2015/07/crispr-dna-editing-2/|title=The Genesis Engine | last = Maxmen | first = Amy | name-list-format = vanc | date = August 2015 | website = WIRED | access-date = 2016-06-05 }}</ref> was the [[American Association for the Advancement of Science|AAAS]]'s choice for breakthrough of the year in 2015.<ref>{{cite web | vauthors = Travis J | title = Breakthrough of the Year: CRISPR makes the cut | url = http://www.sciencemag.org/news/2015/12/and-science-s-breakthrough-year | work = Science Magazine | publisher = American Association for the Advancement of Science | date = 17 December 2015 }}</ref> [[Bioethical]] concerns have been raised about the prospect of using CRISPR for [[germline]] editing.<ref>{{cite journal | vauthors = Ledford H | title = CRISPR, the disruptor | journal = Nature | volume = 522 | issue = 7554 | pages = 20–4 | date = June 2015 | pmid = 26040877 | doi = 10.1038/522020a }}</ref> |
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{{Infobox nonhuman protein |
{{Infobox nonhuman protein |
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| Name = Cascade (CRISPR-associated complex for antiviral defense) |
| Name = Cascade (CRISPR-associated complex for antiviral defense) |
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| image = |
| image = 4QYZ.png |
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| caption = CRISPR Cascade protein (cyan) bound to CRISPR RNA (green) and phage DNA (red)<ref name="Mulepati_2014">{{PDB|4QYZ}}: {{cite journal | vauthors = Mulepati S, Héroux A, Bailey S| title = Crystal structure of a CRISPR RNA–guided surveillance complex bound to a ssDNA target| journal = Science | volume = 345 | issue = 6203 | pages = 1479–1484 | year = 2014 | pmid = 25123481 | pmc = 4427192| doi = 10.1126/science.1256996 | bibcode = 2014Sci...345.1479M}}</ref> |
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| width = 320 |
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| Organism = ''Escherichia coli'' |
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| caption =Structure of crRNA-guided E. coli Cascade complex (Cas, blue) bound to single-stranded DNA (orange). |
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| TaxID = 511145 |
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| Organism = Escherichia coli |
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| |
| Symbol = CRISPR |
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| EntrezGene = 947229 |
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| ATC_prefix = |
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| ATC_suffix = |
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| ATC_supplemental = |
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| CAS_number = |
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| CAS_supplemental = |
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| DrugBank = |
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| EntrezGene = |
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| HomoloGene = |
| HomoloGene = |
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| PDB =4QYZ |
| PDB = 4QYZ |
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| UniProt = P38036 |
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| RefSeqmRNA = |
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| RefSeqProtein = NP_417241.1 |
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}} |
}} |
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{{CRISPR}} |
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{{Genetic engineering sidebar}} |
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'''CRISPR''' ({{IPAc-en|ˈ|k|r|ɪ|s|p|ər}}) (an [[acronym]] for '''c'''lustered '''r'''egularly '''i'''nterspaced '''s'''hort '''p'''alindromic '''r'''epeats) is a family of [[DNA]] sequences found in the [[genome]]s of [[prokaryotic]] organisms such as [[bacteria]] and [[archaea]].<ref name="pmid25574773"/> Each sequence within an individual prokaryotic cell is derived from a DNA fragment of a [[bacteriophage]] that had previously infected the prokaryote or one of its ancestors.<ref name="Hille2018"/><ref>{{cite journal |last1=Rath |first1=Devashish |last2=Amlinger |first2=Lina |last3=Rath |first3=Archana |last4=Lundgren |first4=Magnus |title=The CRISPR-Cas immune system: Biology, mechanisms and applications |journal=Biochimie |date=October 2015 |volume=117 |pages=119–128 |doi=10.1016/j.biochi.2015.03.025 |pmid=25868999 }}</ref> These sequences are used to detect and destroy DNA from similar bacteriophages during subsequent infections. Hence these sequences play a key role in the antiviral (i.e. anti-[[Bacteriophage|phage]]) defense system of prokaryotes and provide a form of heritable,<ref name="Hille2018"/> [[acquired immunity]].<ref name="pmid25574773">{{cite journal | vauthors = Barrangou R | author-link=Rodolphe Barrangou | title = The roles of CRISPR-Cas systems in adaptive immunity and beyond | journal = Current Opinion in Immunology | volume = 32 | pages = 36–41 | year = 2015 | pmid = 25574773 | doi = 10.1016/j.coi.2014.12.008 }}</ref><ref>{{cite journal | vauthors = Redman M, King A, Watson C, King D | title = What is CRISPR/Cas9? | journal = Archives of Disease in Childhood: Education and Practice Edition | volume = 101 | issue = 4 | pages = 213–215 | date = August 2016 | pmid = 27059283 | pmc = 4975809 | doi = 10.1136/archdischild-2016-310459 }}</ref><ref name="pmid17379808">{{cite journal | vauthors = Barrangou R, Fremaux C, Deveau H, Richards M, Boyaval P, Moineau S, Romero DA, Horvath P | author-link1=Rodolphe Barrangou | title = CRISPR provides acquired resistance against viruses in prokaryotes | journal = Science | volume = 315 | issue = 5819 | pages = 1709–1712 | date = March 2007 | pmid = 17379808 | doi = 10.1126/science.1138140 | bibcode = 2007Sci...315.1709B | hdl=20.500.11794/38902 | hdl-access = free }} {{Registration required}}</ref><ref name="pmid19095942">{{cite journal | vauthors = Marraffini LA, Sontheimer EJ | title = CRISPR interference limits horizontal gene transfer in staphylococci by targeting DNA | journal = Science | volume = 322 | issue = 5909 | pages = 1843–1845 | date = December 2008 | pmid = 19095942 | pmc = 2695655 | doi = 10.1126/science.1165771 | bibcode = 2008Sci...322.1843M }}</ref> CRISPR is found in approximately 50% of sequenced [[bacterial genome]]s and nearly 90% of sequenced archaea.<ref name="Hille2018">{{cite journal |vauthors=Hille F, Richter H, Wong SP, Bratovič M, Ressel S, Charpentier E |title=The Biology of CRISPR-Cas: Backward and Forward |journal=Cell |volume=172 |issue=6 |pages=1239–1259 |date=March 2018 |pmid=29522745 |doi=10.1016/j.cell.2017.11.032 |hdl=21.11116/0000-0003-FC0D-4 |hdl-access=free }}</ref> |
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[[File:Crispr.png|thumb|Diagram of the CRISPR prokaryotic antiviral defense mechanism<ref>{{cite journal | vauthors = Horvath P, Barrangou R | author-link2=Rodolphe Barrangou | title = CRISPR/Cas, the immune system of bacteria and archaea | journal = Science | volume = 327 | issue = 5962 | pages = 167–170 | date = January 2010 | pmid = 20056882 | doi = 10.1126/science.1179555 | bibcode=2010Sci...327..167H }}</ref>]] |
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[[Cas9]] (or "CRISPR-associated protein 9") is an [[enzyme]] that uses CRISPR sequences as a guide to recognize and open up specific strands of DNA that are complementary to the CRISPR sequence. Cas9 enzymes together with CRISPR sequences form the basis of a technology known as [[CRISPR gene editing|CRISPR-Cas9]] that can be used to edit genes within living organisms.<ref>{{cite journal | vauthors = Bak RO, Gomez-Ospina N, Porteus MH | title = Gene Editing on Center Stage | journal = Trends in Genetics | volume = 34 | issue = 8 | pages = 600–611 | date = August 2018 | pmid = 29908711 | doi = 10.1016/j.tig.2018.05.004 }}</ref><ref name="pmid24651067">{{cite journal | vauthors = Zhang F, Wen Y, Guo X | title = CRISPR/Cas9 for genome editing: progress, implications and challenges | journal = Human Molecular Genetics | volume = 23 | issue = R1 | pages = R40–6 | year = 2014 | pmid = 24651067 | doi = 10.1093/hmg/ddu125 | doi-access = free }}</ref> This editing process has a wide variety of applications including basic biological research, development of [[biotechnology|biotechnological]] products, and treatment of diseases.<ref>CRISPR-CAS9, TALENS and ZFNS – the battle in gene editing https://www.ptglab.com/news/blog/crispr-cas9-talens-and-zfns-the-battle-in-gene-editing/ {{Webarchive|url=https://web.archive.org/web/20210525031855/https://www.ptglab.com/news/blog/crispr-cas9-talens-and-zfns-the-battle-in-gene-editing/ |date=2021-05-25 }}</ref><ref name="Hsu2014"/> The development of the CRISPR-Cas9 genome editing technique was recognized by the [[Nobel Prize in Chemistry]] in 2020 awarded to [[Emmanuelle Charpentier]] and [[Jennifer Doudna]].<ref>{{cite web |title=Press release: The Nobel Prize in Chemistry 2020 |url=https://www.nobelprize.org/prizes/chemistry/2020/press-release/ |publisher=Nobel Foundation |access-date=7 October 2020 |archive-date=15 January 2021 |archive-url=https://web.archive.org/web/20210115172618/https://www.nobelprize.org/prizes/chemistry/2020/press-release/ |url-status=live }}</ref><ref name="NYT-20201007">{{cite news |vauthors=Wu KJ, Peltier E |title=Nobel Prize in Chemistry Awarded to 2 Scientists for Work on Genome Editing – Emmanuelle Charpentier and Jennifer A. Doudna developed the Crispr tool, which can alter the DNA of animals, plants and microorganisms with high precision. |url=https://www.nytimes.com/2020/10/07/science/nobel-prize-chemistry-crispr.html |date=7 October 2020 |work=[[The New York Times]] |access-date=7 October 2020 |archive-date=8 October 2020 |archive-url=https://web.archive.org/web/20201008094313/https://www.nytimes.com/2020/10/07/science/nobel-prize-chemistry-crispr.html |url-status=live }}</ref> |
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== History == |
== History == |
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=== Repeated sequences === |
=== Repeated sequences === |
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The discovery of clustered DNA repeats |
The discovery of clustered DNA repeats took place independently in three parts of the world. The first description of what would later be called CRISPR is from [[Osaka University]] researcher [[Yoshizumi Ishino]] and his colleagues in 1987. They accidentally cloned part of a CRISPR sequence together with the "''iap" gene'' ''(isozyme conversion of alkaline phosphatase)'' from their target genome, that of ''[[Escherichia coli]]''.<ref>{{cite journal | vauthors = Rawat A, Roy M, Jyoti A, Kaushik S, Verma K, Srivastava VK | title = Cysteine proteases: Battling pathogenic parasitic protozoans with omnipresent enzymes | journal = Microbiological Research | volume = 249 | page = 126784 | date = August 2021 | pmid = 33989978 | doi = 10.1016/j.micres.2021.126784 | doi-access = free }}</ref><ref name="Ishino-1987">{{cite journal | vauthors = Ishino Y, Shinagawa H, Makino K, Amemura M, Nakata A | title = Nucleotide sequence of the iap gene, responsible for alkaline phosphatase isozyme conversion in Escherichia coli, and identification of the gene product | journal = Journal of Bacteriology | volume = 169 | issue = 12 | pages = 5429–5433 | date = December 1987 | pmid = 3316184 | pmc = 213968 | doi = 10.1128/jb.169.12.5429-5433.1987 }}</ref> The organization of the repeats was unusual. Repeated sequences are typically arranged consecutively, without interspersing different sequences.<ref name="Hsu2014"/><ref name="Ishino-1987"/> They did not know the function of the interrupted clustered repeats. |
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In 1993 researchers of ''[[Mycobacterium tuberculosis]]'' in the Netherlands published two articles about a cluster of interrupted direct |
In 1993, researchers of ''[[Mycobacterium tuberculosis]]'' in the Netherlands published two articles about a cluster of interrupted [[direct repeat]]s (DR) in that bacterium. They recognized the diversity of the sequences that intervened in the direct repeats among different strains of ''M. tuberculosis''<ref name="Soolingen1993">{{cite journal | vauthors = van Soolingen D, de Haas PE, Hermans PW, Groenen PM, van Embden JD | title = Comparison of various repetitive DNA elements as genetic markers for strain differentiation and epidemiology of Mycobacterium tuberculosis | journal = Journal of Clinical Microbiology | volume = 31 | issue = 8 | pages = 1987–1995 | date = August 1993 | pmid = 7690367 | pmc = 265684 | doi = 10.1128/JCM.31.8.1987-1995.1993 }}</ref> and used this property to design a typing method called ''[[wikt:spoligotyping|spoligotyping]]'', still in use today.<ref name="Groenen1993">{{cite journal | vauthors = Groenen PM, Bunschoten AE, van Soolingen D, van Embden JD | title = Nature of DNA polymorphism in the direct repeat cluster of Mycobacterium tuberculosis; application for strain differentiation by a novel typing method | journal = Molecular Microbiology | volume = 10 | issue = 5 | pages = 1057–1065 | date = December 1993 | pmid = 7934856 | doi = 10.1111/j.1365-2958.1993.tb00976.x }}</ref><ref name="Mojica2016">{{cite journal |vauthors=Mojica FJ, Montoliu L |title=On the Origin of CRISPR-Cas Technology: From Prokaryotes to Mammals |journal=Trends in Microbiology |volume=24 |issue=10 |pages=811–820 |year=2016 |pmid=27401123 |doi=10.1016/j.tim.2016.06.005 }}</ref> |
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[[Francisco Mojica]] at the [[University of Alicante]] in Spain studied the function of repeats in the archaeal species ''[[Haloferax]]'' and ''[[Haloarcula]]''. Mojica's supervisor surmised that the clustered repeats had a role in correctly segregating replicated DNA into daughter cells during cell division, because plasmids and chromosomes with identical repeat arrays could not coexist in ''[[Haloferax volcanii]]''. Transcription of the interrupted repeats was also noted for the first time; this was the first full characterization of CRISPR.<ref name="Mojica2016"/><ref name="Mojica2016b">{{cite journal |vauthors=Mojica FJ, Rodriguez-Valera F |title=The discovery of CRISPR in archaea and bacteria |journal=The FEBS Journal |volume=283 |issue=17 |pages=3162–3169 |year=2016 |pmid=27234458 |doi=10.1111/febs.13766 |hdl=10045/57676 |hdl-access=free }}</ref> By 2000, Mojica and his students, after an automated search of published genomes, identified interrupted repeats in 20 species of microbes as belonging to the same family.<ref name="Mojica_2000">{{cite journal | vauthors = Mojica FJ, Díez-Villaseñor C, Soria E, Juez G | title = Biological significance of a family of regularly spaced repeats in the genomes of Archaea, Bacteria and mitochondria | journal = Molecular Microbiology | volume = 36 | issue = 1 | pages = 244–246 | date = April 2000 | pmid = 10760181 | doi = 10.1046/j.1365-2958.2000.01838.x |doi-access=free}}</ref> Because those sequences were interspaced, Mojica initially called these sequences "short regularly spaced repeats" (SRSR).<ref>{{cite book |vauthors=Isaacson W |author-link1=Walter Isaacson |title=The Code Breaker: Jennifer Doudna, Gene Editing, and the Future of the Human Race |url=https://books.google.com/books?id=f_D3DwAAQBAJ |page=73 |location=New York |publisher=Simon & Schuster |year=2021 |isbn=978-1-9821-1585-2 |oclc=1239982737 |access-date=2021-10-20 |archive-date=2023-01-14 |archive-url=https://web.archive.org/web/20230114155931/https://books.google.com/books?id=f_D3DwAAQBAJ |url-status=live }}</ref> In 2001, Mojica and [[Ruud Jansen]], who were searching for an additional interrupted repeats, proposed the acronym CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) to unify the numerous acronyms used to describe these sequences.<ref name="Mojica2016b"/><ref>{{cite book | vauthors = Barrangou R, van der Oost J | author-link1 = Rodolphe Barrangou | title = CRISPR-Cas Systems: RNA-mediated Adaptive Immunity in Bacteria and Archaea | date = 2013 | publisher = Springer | location = Heidelberg | isbn = 978-3-642-34656-9 | page = 6 }}</ref> In 2002, Tang, et al. showed evidence that CRISPR repeat regions from the genome of ''[[Archaeoglobus fulgidus]]'' were transcribed into long RNA molecules subsequently processed into unit-length small RNAs, plus some longer forms of 2, 3, or more spacer-repeat units.<ref name="pmid12032318">{{cite journal | vauthors = Tang TH, Bachellerie JP, Rozhdestvensky T, Bortolin ML, Huber H, Drungowski M, Elge T, Brosius J, Hüttenhofer A | title = Identification of 86 candidates for small non-messenger RNAs from the archaeon Archaeoglobus fulgidus | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 99 | issue = 11 | pages = 7536–7541 | date = May 2002 | pmid = 12032318 | pmc = 124276 | doi = 10.1073/pnas.112047299 | doi-access = free | bibcode = 2002PNAS...99.7536T }}</ref><ref name="pmid25994611">{{cite journal | vauthors = Charpentier E, Richter H, van der Oost J, White MF | title = Biogenesis pathways of RNA guides in archaeal and bacterial CRISPR-Cas adaptive immunity | journal = FEMS Microbiology Reviews | volume = 39 | issue = 3 | pages = 428–441 | date = May 2015 | pmid = 25994611 | pmc = 5965381 | doi = 10.1093/femsre/fuv023 }}</ref> |
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In 2005, [[yogurt]] researcher [[Rodolphe Barrangou]] discovered that ''[[Streptococcus thermophilus]]'', after iterative phage infection challenges, develops increased phage resistance due to the incorporation of additional CRISPR spacer sequences.<ref name="Romero_2020">{{cite journal | vauthors = Romero DA, Magill D, Millen A, Horvath P, Fremaux C | title = Dairy lactococcal and streptococcal phage-host interactions: an industrial perspective in an evolving phage landscape | journal = FEMS Microbiology Reviews | volume = 44 | issue = 6 | pages = 909–932 | date = November 2020 | pmid = 33016324 | doi = 10.1093/femsre/fuaa048 | doi-access = }}</ref> Barrangou's employer, the Danish food company Danisco, then developed phage-resistant ''S. thermophilus'' strains for yogurt production. Danisco was later bought by [[DuPont]], which owns about 50 percent of the global dairy culture market, and the technology spread widely.<ref name="rbpont">{{cite news |vauthors=Molteni M, Huckins G |title=The WIRED Guide to Crispr |url=https://www.wired.com/story/wired-guide-to-crispr/ |agency=Wired Magazine |publisher=Condé Nast |date=1 August 2020 |access-date=23 February 2021 |archive-date=23 October 2021 |archive-url=https://web.archive.org/web/20211023062846/https://www.wired.com/story/wired-guide-to-crispr/ |url-status=live }}</ref> |
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=== CRISPR-associated systems === |
=== CRISPR-associated systems === |
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A major |
A major advance in understanding CRISPR came with Jansen's observation that the prokaryote repeat cluster was accompanied by four homologous genes that make up CRISPR-associated systems, ''cas'' 1–4. The Cas proteins showed [[helicase]] and [[nuclease]] [[Structural motif|motifs]], suggesting a role in the dynamic structure of the CRISPR loci.<ref name="pmid11952905">{{cite journal | vauthors = Jansen R, Embden JD, Gaastra W, Schouls LM | title = Identification of genes that are associated with DNA repeats in prokaryotes | journal = Molecular Microbiology | volume = 43 | issue = 6 | pages = 1565–1575 | date = March 2002 | pmid = 11952905 | doi = 10.1046/j.1365-2958.2002.02839.x | doi-access = free }}</ref> In this publication, the acronym CRISPR was used as the universal name of this pattern, but its function remained enigmatic. |
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[[File:SimpleCRISPR.jpg|thumb|Simplified diagram of a CRISPR locus. The three major components of a CRISPR locus are shown: ''cas'' genes, a leader sequence, and a repeat-spacer array. Repeats are shown as gray boxes and spacers are colored bars. The arrangement of the three components is not always as shown.<ref name="pmid20056882">{{cite journal | vauthors = Horvath P, Barrangou R | title = CRISPR/Cas, the immune system of bacteria and archaea | journal = Science | volume = 327 | issue = 5962 | pages = |
[[File:SimpleCRISPR.jpg|thumb|Simplified diagram of a CRISPR locus. The three major components of a CRISPR locus are shown: ''cas'' genes, a leader sequence, and a repeat-spacer array. Repeats are shown as gray boxes and spacers are colored bars. The arrangement of the three components is not always as shown.<ref name="pmid20056882">{{cite journal | vauthors = Horvath P, Barrangou R | author-link2=Rodolphe Barrangou | title = CRISPR/Cas, the immune system of bacteria and archaea | journal = Science | volume = 327 | issue = 5962 | pages = 167–170 | date = January 2010 | pmid = 20056882 | doi = 10.1126/Science.1179555 | bibcode = 2010Sci...327..167H }}</ref><ref name="pmid20125085">{{cite journal | vauthors = Marraffini LA, Sontheimer EJ | title = CRISPR interference: RNA-directed adaptive immunity in bacteria and archaea | journal = Nature Reviews Genetics | volume = 11 | issue = 3 | pages = 181–190 | date = March 2010 | pmid = 20125085 | pmc = 2928866 | doi = 10.1038/nrg2749 }}</ref> |
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In addition, several CRISPRs with similar sequences can be present in a single genome, only one of which is associated with ''cas'' genes.<ref name="pmid17521438" />]] |
In addition, several CRISPRs with similar sequences can be present in a single genome, only one of which is associated with ''cas'' genes.<ref name="pmid17521438">{{cite journal | vauthors = Grissa I, Vergnaud G, Pourcel C | title = The CRISPRdb database and tools to display CRISPRs and to generate dictionaries of spacers and repeats | journal = BMC Bioinformatics | volume = 8 | page = 172 | date = May 2007 | pmid = 17521438 | pmc = 1892036 | doi = 10.1186/1471-2105-8-172 | doi-access = free }}</ref>]] |
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In 2005, three independent research groups showed that some CRISPR spacers are derived from [[phage]] DNA and [[extrachromosomal DNA]] such as [[ |
In 2005, three independent research groups showed that some CRISPR spacers are derived from [[phage]] DNA and [[extrachromosomal DNA]] such as [[plasmid]]s.<ref name="pmid15758212">{{cite journal | vauthors = Pourcel C, Salvignol G, Vergnaud G | title = CRISPR elements in Yersinia pestis acquire new repeats by preferential uptake of bacteriophage DNA, and provide additional tools for evolutionary studies | journal = Microbiology | volume = 151 | issue = Pt 3 | pages = 653–663 | date = March 2005 | pmid = 15758212 | doi = 10.1099/mic.0.27437-0 | doi-access = free }}</ref><ref name="pmid15791728">{{cite journal | vauthors = Mojica FJ, Díez-Villaseñor C, García-Martínez J, Soria E | title = Intervening sequences of regularly spaced prokaryotic repeats derive from foreign genetic elements | journal = Journal of Molecular Evolution | volume = 60 | issue = 2 | pages = 174–182 | date = February 2005 | pmid = 15791728 | doi = 10.1007/s00239-004-0046-3 | bibcode = 2005JMolE..60..174M }}</ref><ref name="pmid16079334">{{cite journal | vauthors = Bolotin A, Quinquis B, Sorokin A, Ehrlich SD | title = Clustered regularly interspaced short palindrome repeats (CRISPRs) have spacers of extrachromosomal origin | journal = Microbiology | volume = 151 | issue = Pt 8 | pages = 2551–2561 | date = August 2005 | pmid = 16079334 | doi = 10.1099/mic.0.28048-0 |doi-access=free}}</ref> In effect, the spacers are fragments of DNA gathered from viruses that previously attacked the cell. The source of the spacers was a sign that the CRISPR-''cas'' system could have a role in adaptive immunity in [[bacteria]].<ref name="pmid20056882"/><ref name="pmid25963251">{{cite journal | vauthors = Morange M | title = What history tells us XXXVII. CRISPR-Cas: The discovery of an immune system in prokaryotes | journal = Journal of Biosciences | volume = 40 | issue = 2 | pages = 221–223 | date = June 2015 | pmid = 25963251 | doi = 10.1007/s12038-015-9532-6 | doi-access = free }}</ref> All three studies proposing this idea were initially rejected by high-profile journals, but eventually appeared in other journals.<ref name="Lander_2016">{{cite journal | vauthors = Lander ES | title = The Heroes of CRISPR | journal = Cell | volume = 164 | issue = 1–2 | pages = 18–28 | date = January 2016 | pmid = 26771483 | doi = 10.1016/j.cell.2015.12.041 | doi-access = free }}</ref> |
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The first publication<ref name="pmid15791728" |
The first publication<ref name="pmid15791728"/> proposing a role of CRISPR-Cas in microbial immunity, by Mojica and collaborators at the [[University of Alicante]], predicted a role for the RNA transcript of spacers on target recognition in a mechanism that could be analogous to the [[RNA interference]] system used by eukaryotic cells. Koonin and colleagues extended this RNA interference hypothesis by proposing mechanisms of action for the different CRISPR-Cas subtypes according to the predicted function of their proteins.<ref name="Makarova2006">{{cite journal | vauthors = Makarova KS, Grishin NV, Shabalina SA, Wolf YI, Koonin EV | author-link5=Eugene Koonin | title = A putative RNA-interference-based immune system in prokaryotes: computational analysis of the predicted enzymatic machinery, functional analogies with eukaryotic RNAi, and hypothetical mechanisms of action | journal = Biology Direct | volume = 1 | page = 7 | date = March 2006 | pmid = 16545108 | pmc = 1462988 | doi = 10.1186/1745-6150-1-7 | doi-access=free }}</ref> |
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Experimental work by several groups revealed the basic mechanisms of CRISPR-Cas immunity. In 2007 the first experimental evidence that CRISPR was an adaptive immune system was published.<ref name= |
Experimental work by several groups revealed the basic mechanisms of CRISPR-Cas immunity. In 2007, the first experimental evidence that CRISPR was an adaptive immune system was published.<ref name="pmid17379808"/><ref name="Hsu2014"/> A CRISPR region in ''[[Streptococcus thermophilus]]'' acquired spacers from the DNA of an infecting [[bacteriophage]]. The researchers manipulated the resistance of ''S. thermophilus'' to different types of phages by adding and deleting spacers whose sequence matched those found in the tested phages.<ref name="craze">{{cite journal | vauthors = Pennisi E | author-link = Elizabeth Pennisi | title = The CRISPR craze | journal = Science | volume = 341 | issue = 6148 | pages = 833–836 | date = August 2013 | pmid = 23970676 | doi = 10.1126/science.341.6148.833 | department = News Focus | bibcode = 2013Sci...341..833P }}</ref><ref name="Marraffini2015"/> In 2008, Brouns and Van der Oost identified a complex of Cas proteins called Cascade, that in ''E. coli'' cut the CRISPR RNA precursor within the repeats into mature spacer-containing RNA molecules called [[CRISPR RNA]] (crRNA), which remained bound to the protein complex.<ref>{{cite journal | vauthors = Brouns SJ, Jore MM, Lundgren M, Westra ER, Slijkhuis RJ, Snijders AP, Dickman MJ, Makarova KS, Koonin EV, van der Oost J | author-link9=Eugene Koonin | title = Small CRISPR RNAs guide antiviral defense in prokaryotes | journal = Science | volume = 321 | issue = 5891 | pages = 960–964 | date = August 2008 | pmid = 18703739 | pmc = 5898235 | doi = 10.1126/science.1159689 | bibcode = 2008Sci...321..960B }}</ref> Moreover, it was found that Cascade, crRNA and a helicase/nuclease ([[Cas3]]) were required to provide a bacterial host with immunity against infection by a [[DNA virus]]. By designing an anti-virus CRISPR, they demonstrated that two orientations of the crRNA (sense/antisense) provided immunity, indicating that the crRNA guides were targeting [[dsDNA]]. That year Marraffini and Sontheimer confirmed that a CRISPR sequence of ''[[S. epidermidis]]'' targeted DNA and not RNA to prevent [[Bacterial conjugation|conjugation]]. This finding was at odds with the proposed RNA-interference-like mechanism of CRISPR-Cas immunity, although a CRISPR-Cas system that targets foreign RNA was later found in ''[[Pyrococcus furiosus]]''.<ref name="Hsu2014"/><ref name="Marraffini2015"/> A 2010 study showed that CRISPR-Cas cuts strands of both phage and plasmid DNA in ''S. thermophilus''.<ref name="Garneau2010">{{cite journal | vauthors = Garneau JE, Dupuis MÈ, Villion M, Romero DA, Barrangou R, Boyaval P, Fremaux C, Horvath P, Magadán AH, Moineau S | author-link5=Rodolphe Barrangou | title = The CRISPR/Cas bacterial immune system cleaves bacteriophage and plasmid DNA | journal = Nature | volume = 468 | issue = 7320 | pages = 67–71 | date = November 2010 | pmid = 21048762 | doi = 10.1038/nature09523 | bibcode = 2010Natur.468...67G }}</ref> |
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=== Cas9 === |
=== Cas9 === |
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{{main|Cas9}} |
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Researchers studied a simpler CRISPR system from ''[[Streptococcus pyogenes]]'' that relies on the protein [[Cas9]]. The Cas9 endonuclease is a four-component system that includes two small RNA molecules named CRISPR RNA (crRNA) and trans-activating CRISPR RNA (tracrRNA).<ref name="Barrangou2015">{{cite journal | vauthors = Barrangou R | title = Diversity of CRISPR-Cas immune systems and molecular machines | journal = Genome Biology | volume = 16 | issue = | pages = 247 | date = November 2015 | pmid = 26549499 | pmc = 4638107 | doi = 10.1186/s13059-015-0816-9 }}</ref> [[Jennifer Doudna]] and [[Emmanuelle Charpentier]] re-engineered the Cas9 endonuclease into a more manageable two-component system by fusing the two RNA molecules into a "single-guide RNA" that, when combined with Cas9, could find and cut the DNA target specified by the guide RNA. By manipulating the nucleotide sequence of the guide RNA, the artificial Cas9 system could be programmed to target any DNA sequence for cleavage.<ref name="pmid22745249" /> Another group of collaborators comprising [[Virginijus Siksnys|Šikšnys]] together with Gasiūnas, Barrangou and Horvath showed that Cas9 from the ''S. thermophilus'' CRISPR system can also be reprogrammed to target a site of their choosing by changing the sequence of its crRNA. These advances fueled efforts to edit genomes with the modified CRISPR-Cas9 system.<ref name="Mojica2016"/> |
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A simpler CRISPR system from ''[[Streptococcus pyogenes]]'' relies on the protein [[Cas9]]. The Cas9 [[endonuclease]] is a four-component system that includes two small molecules: crRNA and trans-activating CRISPR RNA (tracrRNA).<ref name="Deltcheva2011">{{cite journal | vauthors = Deltcheva E, Chylinski K, Sharma CM, Gonzales K, Chao Y, Pirzada ZA, Eckert MR, Vogel J, Charpentier E | title = CRISPR RNA maturation by trans-encoded small RNA and host factor RNase III | journal = Nature | volume = 471 | issue = 7340 | pages = 602–607 | date = March 2011 | pmid = 21455174 | pmc = 3070239 | doi = 10.1038/nature09886 | bibcode = 2011Natur.471..602D }}</ref><ref name="Barrangou2015">{{cite journal | vauthors = Barrangou R | author-link=Rodolphe Barrangou | title = Diversity of CRISPR-Cas immune systems and molecular machines | journal = Genome Biology | volume = 16 | page = 247 | date = November 2015 | pmid = 26549499 | pmc = 4638107 | doi = 10.1186/s13059-015-0816-9 | doi-access=free }}</ref> In 2012, [[Jennifer Doudna]] and [[Emmanuelle Charpentier]] re-engineered the Cas9 endonuclease into a more manageable two-component system by fusing the two RNA molecules into a "[[Guide_RNA#Structure|single-guide RNA]]" that, when combined with Cas9, could find and cut the DNA target specified by the guide RNA.<ref name="pmid22745249">{{cite journal | vauthors = Jinek M, Chylinski K, Fonfara I, Hauer M, Doudna JA, Charpentier E | author-link5=Jennifer Doudna | title = A programmable dual-RNA-guided DNA endonuclease in adaptive bacterial immunity | journal = Science | volume = 337 | issue = 6096 | pages = 816–821 | date = August 2012 | pmid = 22745249 | pmc = 6286148| doi = 10.1126/science.1225829 | bibcode = 2012Sci...337..816J }}</ref> This contribution was so significant that it was recognized by the [[Nobel Prize in Chemistry]] in 2020. By manipulating the nucleotide sequence of the guide RNA, the artificial Cas9 system could be programmed to target any DNA sequence for separation.<ref name="pmid22745249"/> Another collaboration comprising [[Virginijus Šikšnys]], Gasiūnas, Barrangou, and Horvath showed that Cas9 from the ''S. thermophilus'' CRISPR system can also be reprogrammed to target a site of their choosing by changing the sequence of its crRNA. These advances fueled efforts to edit genomes with the modified CRISPR-Cas9 system.<ref name="Mojica2016"/> |
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Groups led by [[Feng Zhang]] and [[George M. Church|George Church]] simultaneously published descriptions of genome editing in human cell cultures using CRISPR-Cas9 for the first time.<ref name="Hsu2014">{{cite journal | vauthors = Hsu PD, Lander ES, Zhang F | author-link3=Feng Zhang | title = Development and applications of CRISPR-Cas9 for genome engineering | journal = Cell | volume = 157 | issue = 6 | pages = 1262–1278 | date = June 2014 | pmid = 24906146 | pmc = 4343198 | doi = 10.1016/j.cell.2014.05.010 }}</ref><ref name="Cong2013">{{cite journal | vauthors = Cong L, Ran FA, Cox D, Lin S, Barretto R, Habib N, Hsu PD, Wu X, Jiang W, Marraffini LA, Zhang F | author-link11=Feng Zhang | title = Multiplex genome engineering using CRISPR/Cas systems | journal = Science | volume = 339 | issue = 6121 | pages = 819–823 | date = February 2013 | pmid = 23287718 | pmc = 3795411 | doi = 10.1126/science.1231143 | bibcode = 2013Sci...339..819C }}</ref><ref name="Mali2013">{{cite journal | vauthors = Mali P, Yang L, Esvelt KM, Aach J, Guell M, DiCarlo JE, Norville JE, Church GM | title = RNA-guided human genome engineering via Cas9 | journal = Science | volume = 339 | issue = 6121 | pages = 823–826 | date = February 2013 | pmid = 23287722 | pmc = 3712628 | doi = 10.1126/science.1232033 | bibcode = 2013Sci...339..823M }}</ref> It has since been used in a wide range of organisms, including baker's yeast (''[[Saccharomyces cerevisiae]]''),<ref name="ReferenceC">{{cite journal | vauthors = DiCarlo JE, Norville JE, Mali P, Rios X, Aach J, Church GM | title = Genome engineering in ''Saccharomyces cerevisiae'' using CRISPR-Cas systems | journal = Nucleic Acids Research | volume = 41 | issue = 7 | pages = 4336–4343 | date = April 2013 | pmid = 23460208 | pmc = 3627607 | doi = 10.1093/nar/gkt135 }}</ref><ref name="quadauxo">{{cite journal | vauthors = Zhang GC, Kong II, Kim H, Liu JJ, Cate JH, Jin YS | title = Construction of a quadruple auxotrophic mutant of an industrial polyploid ''saccharomyces cerevisiae'' strain by using RNA-guided Cas9 nuclease | journal = Applied and Environmental Microbiology | volume = 80 | issue = 24 | pages = 7694–7701 | date = December 2014 | pmid = 25281382 | pmc = 4249234 | doi = 10.1128/AEM.02310-14 | bibcode = 2014ApEnM..80.7694Z }}</ref><ref name="metaeng">{{cite journal | vauthors = Liu JJ, Kong II, Zhang GC, Jayakody LN, Kim H, Xia PF, Kwak S, Sung BH, Sohn JH, Walukiewicz HE, Rao CV, Jin YS | title = Metabolic Engineering of Probiotic ''Saccharomyces boulardii'' | journal = Applied and Environmental Microbiology | volume = 82 | issue = 8 | pages = 2280–2287 | date = April 2016 | pmid = 26850302 | pmc = 4959471 | doi = 10.1128/AEM.00057-16 | bibcode = 2016ApEnM..82.2280L }}</ref> the [[opportunistic pathogen]] ''[[Candida albicans]]'',<ref name="pmid25977940">{{cite journal | vauthors = Vyas VK, Barrasa MI, Fink GR | title = ''Candida albicans'' CRISPR system permits genetic engineering of essential genes and gene families | journal = Science Advances | volume = 1 | issue = 3 | pages = e1500248 | date = 2015 | pmid = 25977940 | pmc = 4428347 | doi = 10.1126/sciadv.1500248 | bibcode = 2015SciA....1E0248V }}</ref><ref>{{cite journal | vauthors = Ng H, Dean N | title = ''Candida albicans'' by Increased Single Guide RNA Expression | journal = mSphere | volume = 2 | issue = 2 | pages = e00385–16 | year = 2017 | pmid = 28435892 | pmc = 5397569 | doi = 10.1128/mSphere.00385-16 }}</ref> zebrafish (''[[Zebrafish|Danio rerio]]''),<ref>{{cite journal | vauthors = Hwang WY, Fu Y, Reyon D, Maeder ML, Tsai SQ, Sander JD, Peterson RT, Yeh JR, Joung JK | title = Efficient genome editing in zebrafish using a CRISPR-Cas system | journal = Nature Biotechnology | volume = 31 | issue = 3 | pages = 227–229 | date = March 2013 | pmid = 23360964 | pmc = 3686313 | doi = 10.1038/nbt.2501 }}</ref> fruit flies (''[[Drosophila melanogaster]]''),<ref>{{cite journal | vauthors = Gratz SJ, Cummings AM, Nguyen JN, Hamm DC, Donohue LK, Harrison MM, Wildonger J, O'Connor-Giles KM | title = Genome engineering of ''Drosophila'' with the CRISPR RNA-guided Cas9 nuclease | journal = Genetics | volume = 194 | issue = 4 | pages = 1029–1035 | date = August 2013 | pmid = 23709638 | pmc = 3730909 | doi = 10.1534/genetics.113.152710 }}</ref><ref>{{cite journal | vauthors = Bassett AR, Tibbit C, Ponting CP, Liu JL | title = Highly efficient targeted mutagenesis of ''Drosophila'' with the CRISPR/Cas9 system | journal = Cell Reports | volume = 4 | issue = 1 | pages = 220–228 | date = July 2013 | pmid = 23827738 | pmc = 3714591 | doi = 10.1016/j.celrep.2013.06.020 }}</ref> ants (''[[Harpegnathos saltator]]''<ref>{{cite journal | vauthors = Yan H, Opachaloemphan C, Mancini G, Yang H, Gallitto M, Mlejnek J, Leibholz A, Haight K, Ghaninia M, Huo L, Perry M, Slone J, Zhou X, Traficante M, Penick CA, Dolezal K, Gokhale K, Stevens K, Fetter-Pruneda I, Bonasio R, Zwiebel LJ, Berger SL, Liebig J, Reinberg D, Desplan C | title = An Engineered orco Mutation Produces Aberrant Social Behavior and Defective Neural Development in Ants | journal = Cell | volume = 170 | issue = 4 | pages = 736–747.e9 | date = August 2017 | pmid = 28802043 | pmc = 5587193 | doi = 10.1016/j.cell.2017.06.051 }}</ref> and ''[[Ooceraea biroi]]''<ref>{{cite journal | vauthors = Trible W, Olivos-Cisneros L, McKenzie SK, Saragosti J, Chang NC, Matthews BJ, Oxley PR, Kronauer DJ | title = orco Mutagenesis Causes Loss of Antennal Lobe Glomeruli and Impaired Social Behavior in Ants | journal = Cell | volume = 170 | issue = 4 | pages = 727–735.e10 | date = August 2017 | pmid = 28802042 | pmc = 5556950 | doi = 10.1016/j.cell.2017.07.001 }}</ref>), mosquitoes (''[[Aedes aegypti]]''<ref>{{cite journal | vauthors = Kistler KE, Vosshall LB, Matthews BJ | title = Genome engineering with CRISPR-Cas9 in the mosquito Aedes aegypti | journal = Cell Reports | volume = 11 | issue = 1 | pages = 51–60 | date = April 2015 | pmid = 25818303 | pmc = 4394034 | doi = 10.1016/j.celrep.2015.03.009 }}</ref>), nematodes (''[[Caenorhabditis elegans]]''),<ref name="Friedland_2013">{{cite journal | vauthors = Friedland AE, Tzur YB, Esvelt KM, Colaiácovo MP, Church GM, Calarco JA | title = Heritable genome editing in C. elegans via a CRISPR-Cas9 system | journal = Nature Methods | volume = 10 | issue = 8 | pages = 741–743 | date = August 2013 | pmid = 23817069 | pmc = 3822328 | doi = 10.1038/nmeth.2532 }}</ref> plants,<ref>{{cite journal | vauthors = Jiang W, Zhou H, Bi H, Fromm M, Yang B, Weeks DP | title = Demonstration of CRISPR/Cas9/sgRNA-mediated targeted gene modification in Arabidopsis, tobacco, sorghum and rice | journal = Nucleic Acids Research | volume = 41 | issue = 20 | pages = e188 | date = November 2013 | pmid = 23999092 | pmc = 3814374 | doi = 10.1093/nar/gkt780 }}</ref> mice (''[[Mus musculus domesticus]])'',<ref name="pmid23643243">{{cite journal | vauthors = Wang H, Yang H, Shivalila CS, Dawlaty MM, Cheng AW, Zhang F, Jaenisch R | author-link6=Feng Zhang | title = One-step generation of mice carrying mutations in multiple genes by CRISPR/Cas-mediated genome engineering | journal = Cell | volume = 153 | issue = 4 | pages = 910–918 | date = May 2013 | pmid = 23643243 | pmc = 3969854 | doi = 10.1016/j.cell.2013.04.025 }}</ref><ref name="Soni_2018">{{cite journal | vauthors = Soni D, Wang DM, Regmi SC, Mittal M, Vogel SM, Schlüter D, Tiruppathi C | title = Deubiquitinase function of A20 maintains and repairs endothelial barrier after lung vascular injury | journal = Cell Death Discovery | volume = 4 | issue = 60 | page = 60| date = May 2018 | pmid = 29796309| pmc =5955943 | doi = 10.1038/s41420-018-0056-3}}</ref> monkeys<ref>{{cite journal | vauthors = Guo X, Li XJ | title = Targeted genome editing in primate embryos | journal = Cell Research | volume = 25 | issue = 7 | pages = 767–768 | date = July 2015 | pmid = 26032266 | pmc = 4493275 | doi = 10.1038/cr.2015.64 }}</ref> and human embryos.<ref name="SCI-20150319">{{cite journal | vauthors = Baltimore D, Berg P, Botchan M, Carroll D, Charo RA, Church G, Corn JE, Daley GQ, Doudna JA, Fenner M, Greely HT, Jinek M, Martin GS, Penhoet E, Puck J, Sternberg SH, Weissman JS, Yamamoto KR | author-link9=Jennifer Doudna | title = Biotechnology. A prudent path forward for genomic engineering and germline gene modification | journal = Science | volume = 348 | issue = 6230 | pages = 36–38 | date = April 2015 | pmid = 25791083 | pmc = 4394183 | doi = 10.1126/science.aab1028 | bibcode = 2015Sci...348...36B }}</ref> |
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CRISPR has been modified to make programmable [[transcription factors]] that allows activation or silencing of targeted genes.<ref>{{cite journal | vauthors = Larson MH, Gilbert LA, Wang X, Lim WA, Weissman JS, Qi LS | title = CRISPR interference (CRISPRi) for sequence-specific control of gene expression | journal = Nature Protocols | volume = 8 | issue = 11 | pages = 2180–2196 | date = November 2013|pmc=3922765| pmid = 24136345 | doi = 10.1038/nprot.2013.132 }}</ref> |
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[[Feng Zhang]]'s and [[George M. Church|George Church]]'s groups simultaneously described genome editing in human cell cultures using CRISPR-Cas9 for the first time.<ref name=Hsu2014>{{cite journal | vauthors = Hsu PD, Lander ES, Zhang F | title = Development and applications of CRISPR-Cas9 for genome engineering | journal = Cell | volume = 157 | issue = 6 | pages = 1262–78 | date = June 2014 | pmid = 24906146 | pmc = 4343198 | doi = 10.1016/j.cell.2014.05.010 }}</ref><ref name=Cong2013>{{cite journal | vauthors = Cong L, Ran FA, Cox D, Lin S, Barretto R, Habib N, Hsu PD, Wu X, Jiang W, Marraffini LA, Zhang F | title = Multiplex genome engineering using CRISPR/Cas systems | journal = Science | volume = 339 | issue = 6121 | pages = 819–23 | date = February 2013 | pmid = 23287718 | pmc = 3795411 | doi = 10.1126/science.1231143 }}</ref><ref name=Mali2013>{{cite journal | vauthors = Mali P, Yang L, Esvelt KM, Aach J, Guell M, DiCarlo JE, Norville JE, Church GM | title = RNA-guided human genome engineering via Cas9 | journal = Science | volume = 339 | issue = 6121 | pages = 823–6 | date = February 2013 | pmid = 23287722 | pmc = 3712628 | doi = 10.1126/science.1232033 }}</ref> It has since been used in a wide range of organisms, including baker's yeast (''[[Saccharomyces cerevisiae]]''),<ref name="ReferenceC">{{cite journal | vauthors = DiCarlo JE, Norville JE, Mali P, Rios X, Aach J, Church GM | title = Genome engineering in Saccharomyces cerevisiae using CRISPR-Cas systems | journal = Nucleic Acids Research | volume = 41 | issue = 7 | pages = 4336–43 | date = April 2013 | pmid = 23460208 | pmc = 3627607 | doi = 10.1093/nar/gkt135 }}</ref><ref name="quadauxo">{{cite journal | vauthors = Zhang GC, Kong II, Kim H, Liu JJ, Cate JH, Jin YS | title = Construction of a quadruple auxotrophic mutant of an industrial polyploid saccharomyces cerevisiae strain by using RNA-guided Cas9 nuclease | journal = Applied and Environmental Microbiology | volume = 80 | issue = 24 | pages = 7694–701 | date = December 2014 | doi = 10.1128/AEM.02310-14 | pmid = 25281382 | pmc=4249234}}</ref><ref name="metaeng">{{cite journal | vauthors = Liu JJ, Kong II, Zhang GC, Jayakody LN, Kim H, Xia PF, Kwak S, Sung BH, Sohn JH, Walukiewicz HE, Rao CV, Jin YS | display-authors = 6 | title = Metabolic Engineering of Probiotic Saccharomyces boulardii | journal = Applied and Environmental Microbiology | volume = 82 | issue = 8 | pages = 2280–7 | date = April 2016 | doi = 10.1128/AEM.00057-16 | pmid = 26850302 | pmc=4959471}}</ref> the opportunistic pathogen ''[[Candida albicans|C. albicans]]'',<ref name="pmid25977940">{{cite journal | vauthors = Vyas VK, Barrasa MI, Fink GR | title = A Candida albicans CRISPR system permits genetic engineering of essential genes and gene families | journal = Science Advances | volume = 1 | issue = 3 | pages = e1500248 | date = 2015 | pmid = 25977940 | pmc = 4428347 | doi = 10.1126/sciadv.1500248 }}</ref><ref>{{cite journal|url = https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5397569/pdf/mSphere.00385-16.pdf | pmc=5397569 | pmid=28435892 | doi=10.1128/mSphere.00385-16 | volume=2 | issue=2 | pages=e00385–16 | title=Dramatic Improvement of CRISPR/Cas9 Editing in ''Candida albicans'' by Increased Single Guide RNA Expression | year=2017 | journal=MSphere | vauthors=Ng H, Dean N}}</ref> zebrafish (''[[Zebrafish|D. rerio]]''),<ref>{{cite journal | vauthors = Hwang WY, Fu Y, Reyon D, Maeder ML, Tsai SQ, Sander JD, Peterson RT, Yeh JR, Joung JK | display-authors = 6 | title = Efficient genome editing in zebrafish using a CRISPR-Cas system | journal = Nature Biotechnology | volume = 31 | issue = 3 | pages = 227–9 | date = March 2013 | pmid = 23360964 | pmc = 3686313 | doi = 10.1038/nbt.2501 }}</ref> fruit flies (''[[Drosophila melanogaster]]''),<ref>{{cite journal | vauthors = Gratz SJ, Cummings AM, Nguyen JN, Hamm DC, Donohue LK, Harrison MM, Wildonger J, O'Connor-Giles KM | title = Genome engineering of Drosophila with the CRISPR RNA-guided Cas9 nuclease | journal = Genetics | volume = 194 | issue = 4 | pages = 1029–35 | date = August 2013 | pmid = 23709638 | pmc = 3730909 | doi = 10.1534/genetics.113.152710 }}</ref> nematodes (''[[Caenorhabditis elegans|C. elegans]]''),<ref name = "Friedland_2013">{{cite journal | vauthors = Friedland AE, Tzur YB, Esvelt KM, Colaiácovo MP, Church GM, Calarco JA | title = Heritable genome editing in C. elegans via a CRISPR-Cas9 system | journal = Nature Methods | volume = 10 | issue = 8 | pages = 741–3 | date = August 2013 | pmid = 23817069 | pmc = 3822328 | doi = 10.1038/nmeth.2532 }}</ref> plants,<ref>{{cite journal | vauthors = Jiang W, Zhou H, Bi H, Fromm M, Yang B, Weeks DP | title = Demonstration of CRISPR/Cas9/sgRNA-mediated targeted gene modification in Arabidopsis, tobacco, sorghum and rice | journal = Nucleic Acids Research | volume = 41 | issue = 20 | pages = e188 | date = November 2013 | pmid = 23999092 | pmc = 3814374 | doi = 10.1093/nar/gkt780 }}</ref> mice,<ref name="pmid23643243">{{cite journal | vauthors = Wang H, Yang H, Shivalila CS, Dawlaty MM, Cheng AW, Zhang F, Jaenisch R | title = One-step generation of mice carrying mutations in multiple genes by CRISPR/Cas-mediated genome engineering | journal = Cell | volume = 153 | issue = 4 | pages = 910–8 | date = May 2013 | pmid = 23643243 | pmc = 3969854 | doi = 10.1016/j.cell.2013.04.025 }}</ref> monkeys<ref>{{cite journal | vauthors = Guo X, Li XJ | title = Targeted genome editing in primate embryos | journal = Cell Research | volume = 25 | issue = 7 | pages = 767–8 | date = July 2015 | pmid = 26032266 | doi = 10.1038/cr.2015.64 | pmc=4493275}}</ref> and human embryos.<ref name="SCI-20150319" /> |
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[[File:Cas12a vs Cas9 cleavage position.svg|thumb|A diagram of the CRISPR nucleases [[Cas12a]] and [[Cas9]] with the position of DNA cleavage shown relative to their [[Protospacer adjacent motif|PAM sequences]] in a zoom-in]] |
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The CRISPR-Cas9 system has been shown to make effective gene edits in Human [[tripronuclear zygotes]], as first described in a 2015 paper by Chinese scientists P. Liang and Y. Xu. The system made a successful cleavage of mutant Beta-Hemoglobin ([[HBB]]) in 28 out of 54 embryos. Four out of the 28 embryos were successfully recombined using a donor template. The scientists showed that during DNA recombination of the cleaved strand, the homologous endogenous sequence HBD competes with the exogenous donor template. DNA repair in human embryos is much more complicated and particular than in derived stem cells.<ref>{{cite journal |vauthors=Liang P, Xu Y, Zhang X, Ding C, Huang R, Zhang Z, Lv J, Xie X, Chen Y, Li Y, Sun Y, Bai Y, Songyang Z, Ma W, Zhou C, Huang J | title = CRISPR/Cas9-mediated gene editing in human tripronuclear zygotes | journal = Protein & Cell | volume = 6 | issue = 5 | pages = 363–372 | date = May 2015 | doi = 10.1007/s13238-015-0153-5 | pmid=25894090 | pmc=4417674}}</ref> |
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=== Cas12a === |
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CRISPR has been modified to make programmable [[transcription factors]] that allow scientists to target and activate or silence specific genes.<ref>{{cite journal | vauthors = Larson MH, Gilbert LA, Wang X, Lim WA, Weissman JS, Qi LS | title = CRISPR interference (CRISPRi) for sequence-specific control of gene expression | journal = Nature Protocols | volume = 8 | issue = 11 | pages = 2180–96 | date = November 2013|pmc=3922765| pmid = 24136345 | doi = 10.1038/nprot.2013.132 }}</ref> |
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{{main|Cas12a}} |
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In 2015, the nuclease [[Cas12a]] (formerly called {{visible anchor|Cpf1}}<ref>{{cite journal | vauthors = Yan MY, Yan HQ, Ren GX, Zhao JP, Guo XP, Sun YC | title = CRISPR-Cas12a-Assisted Recombineering in Bacteria | journal = Applied and Environmental Microbiology | volume = 83 | issue = 17 | date = September 2017 | pmid = 28646112 | pmc = 5561284 | doi = 10.1128/AEM.00947-17 | bibcode = 2017ApEnM..83E.947Y }}</ref>) was characterized in the CRISPR-Cpf1 system of the bacterium ''[[Francisella novicida]]''.<ref name="pmid26422227">{{cite journal | vauthors = Zetsche B, Gootenberg JS, Abudayyeh OO, Slaymaker IM, Makarova KS, Essletzbichler P, Volz SE, Joung J, van der Oost J, Regev A, Koonin EV, Zhang F | title = Cpf1 is a single RNA-guided endonuclease of a class 2 CRISPR-Cas system | journal = Cell | volume = 163 | issue = 3 | pages = 759–771 | date = October 2015 | pmid = 26422227 | pmc = 4638220 | doi = 10.1016/j.cell.2015.09.038 | author-link12 = Eugene Koonin }}</ref><ref name="pmid27096362">{{cite journal | vauthors = Fonfara I, Richter H, Bratovič M, Le Rhun A, Charpentier E | title = The CRISPR-associated DNA-cleaving enzyme Cpf1 also processes precursor CRISPR RNA | journal = Nature | volume = 532 | issue = 7600 | pages = 517–521 | date = April 2016 | pmid = 27096362 | doi = 10.1038/nature17945 | bibcode = 2016Natur.532..517F }}</ref> Its original name, from a [[TIGRFAMs]] [[protein family]] definition built in 2012, reflects the prevalence of its CRISPR-Cas subtype in the ''Prevotella'' and ''Francisella'' lineages. Cas12a showed several key differences from Cas9 including: causing a 'staggered' cut in double stranded DNA as opposed to the 'blunt' cut produced by Cas9, relying on a 'T rich' [[Protospacer adjacent motif|PAM]] (providing alternative targeting sites to Cas9), and requiring only a CRISPR RNA (crRNA) for successful targeting. By contrast, Cas9 requires both crRNA and a [[trans-activating crRNA]] (tracrRNA). |
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These differences may give Cas12a some advantages over Cas9. For example, Cas12a's small crRNAs are ideal for multiplexed genome editing, as more of them can be packaged in one vector than can Cas9's sgRNAs. The sticky 5′ overhangs left by Cas12a can also be used for DNA assembly that is much more target-specific than traditional restriction enzyme cloning.<ref name="PMC5316869">{{cite journal | vauthors = Kim H, Kim ST, Ryu J, Kang BC, Kim JS, and Kim SG | title = CRISPR/Cpf1-mediated DNA-free plant genome editing | journal = Nature Communications | volume = 8 | issue = 14406 | page = 14406 | date = February 2017 | pmc = 5316869 | doi = 10.1038/ncomms14406 | pmid=28205546| bibcode = 2017NatCo...814406K }}</ref> Finally, Cas12a cleaves DNA 18–23 base pairs downstream from the PAM site. This means there is no disruption to the recognition sequence after repair, and so Cas12a enables multiple rounds of DNA cleavage. By contrast, since Cas9 cuts only 3 base pairs upstream of the PAM site, the NHEJ pathway results in [[indel]] mutations that destroy the recognition sequence, thereby preventing further rounds of cutting. In theory, repeated rounds of DNA cleavage should cause an increased opportunity for the desired genomic editing to occur.<ref>{{cite web|title = Cpf1 Nuclease|url = https://www.abmgood.com/marketing/knowledge_base/CRISPR_Cas9_Introduction_Part7.php#ATSPC|website = abmgood.com|access-date = 2017-12-14|archive-date = 2021-10-23|archive-url = https://web.archive.org/web/20211023062846/https://old.abmgood.com/marketing/knowledge_base/CRISPR_Cas9_Introduction_Part7.php#ATSPC|url-status = live}}</ref> A distinctive feature of Cas12a, as compared to Cas9, is that after cutting its target, Cas12a remains bound to the target and then cleaves other ssDNA molecules non-discriminately.<ref>{{cite journal | vauthors = Chen JS, Ma E, Harrington LB, Da Costa M, Tian X, Palefsky JM, Doudna JA | title = CRISPR-Cas12a target binding unleashes indiscriminate single-stranded DNase activity | journal = Science | volume = 360 | issue = 6387 | pages = 436–439 | date = April 2018 | pmid = 29449511 | doi = 10.1126/science.aar6245 | pmc = 6628903 | bibcode = 2018Sci...360..436C | doi-access = free }}</ref> This property is called "collateral cleavage" or "trans-cleavage" activity and has been exploited for the development of various diagnostic technologies.<ref name="CRISPR-Cas12-based detection of SAR">{{cite journal | vauthors = Broughton JP, Deng X, Yu G, Fasching CL, Servellita V, Singh J, Miao X, Streithorst JA, Granados A, Sotomayor-Gonzalez A, Zorn K, Gopez A, Hsu E, Gu W, Miller S, Pan CY, Guevara H, Wadford DA, Chen JS, Chiu CY | title = CRISPR-Cas12-based detection of SARS-CoV-2 | journal = Nature Biotechnology | volume = 38 | issue = 7 | pages = 870–874 | date = July 2020 | pmid = 32300245 | doi = 10.1038/s41587-020-0513-4 | pmc = 9107629 | doi-access = free }}</ref><ref name="Enhancement of trans-cleavage activ">{{cite journal | vauthors = Nguyen LT, Smith BM, Jain PK | title = Enhancement of trans-cleavage activity of Cas12a with engineered crRNA enables amplified nucleic acid detection | journal = Nature Communications | volume = 11 | issue = 1 | page = 4906 | date = September 2020 | pmid = 32999292 | doi = 10.1038/s41467-020-18615-1 | pmc = 7528031 | bibcode = 2020NatCo..11.4906N | doi-access = free }}</ref> |
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The CRIPSR/Cas9 system has shown to make effective gene edits in Human [[tripronuclear zygotes]] first described in a 2015 paper by Chinese scientists P. Liang and Y. Xu. The system made a successful cleavage of mutant [[HBB|Beta-Hemoglobin]] (HBB) in 28 out of 54 embryos. 4 out of the 28 embryos were successfully recombined using a donor template given by the scientists. The scientists showed that during DNA recombination of the cleaved strand, the homologous endogenous sequence HBD competes with the exogenous donor template. DNA repair in human embryos is much more complicated and particular than in derived stem cells.<ref>{{cite journal |vauthors=Liang P, Xu Y, Zhang X, Ding C, Huang R, Zhang Z, Lv J, Xie X, Chen Y, Li Y, Sun Y, Bai Y, Songyang Z, Ma W, Zhou C, Huang J | display-authors = 6 | title = CRISPR/Cas9-mediated gene editing in human tripronuclear zygotes | journal = Protein & cell | volume = 6 | issue = 5 | pages = 363–372 | date = May 2015 | doi = 10.1007/s13238-015-0153-5 | pmid=25894090 | pmc=4417674}}</ref> |
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=== Cas13 === |
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In |
In 2016, the nuclease {{visible anchor|Cas13a}} (formerly known as {{visible anchor|C2c2}}) from the bacterium ''Leptotrichia shahii'' was characterized. Cas13 is an RNA-guided RNA endonuclease, which means that it does not cleave DNA, but only single-stranded RNA. Cas13 is guided by its crRNA to a ssRNA target and binds and cleaves the target. Similar to Cas12a, the Cas13 remains bound to the target and then cleaves other ssRNA molecules non-discriminately.<ref>{{cite journal | vauthors = Abudayyeh OO, Gootenberg JS, Konermann S, Joung J, Slaymaker IM, Cox DB, Shmakov S, Makarova KS, Semenova E, Minakhin L, Severinov K, Regev A, Lander ES, Koonin EV, Zhang F | title = C2c2 is a single-component programmable RNA-guided RNA-targeting CRISPR effector | journal = Science | volume = 353 | issue = 6299 | pages = aaf5573 | date = August 2016 | pmid = 27256883 | pmc = 5127784 | doi = 10.1126/science.aaf5573 }}</ref> This collateral cleavage property has been exploited for the development of various diagnostic technologies.<ref name="Nucleic acid detection with CRISPR">{{cite journal | vauthors = Gootenberg JS, Abudayyeh OO, Lee JW, Essletzbichler P, Dy AJ, Joung J, Verdine V, Donghia N, Daringer NM, Freije CA, Myhrvold C, Bhattacharyya RP, Livny J, Regev A, Koonin EV, Hung DT, Sabeti PC, Collins JJ, Zhang F | title = Nucleic acid detection with CRISPR-Cas13a/C2c2 | journal = Science | volume = 356 | issue = 6336 | pages = 438–442 | date = April 2017 | pmid = 28408723 | pmc = 5526198 | doi = 10.1126/science.aam9321 | bibcode = 2017Sci...356..438G }}</ref><ref>{{cite journal | vauthors = Gootenberg JS, Abudayyeh OO, Kellner MJ, Joung J, Collins JJ, Zhang F | title = Multiplexed and portable nucleic acid detection platform with Cas13, Cas12a, and Csm6 | journal = Science | volume = 360 | issue = 6387 | pages = 439–444 | date = April 2018 | pmid = 29449508 | pmc = 5961727 | doi = 10.1126/science.aaq0179 | bibcode = 2018Sci...360..439G }}</ref><ref name="SPRINT: a Cas13a-based platform for">{{cite journal | vauthors = Iwasaki RS, Batey RT | title = SPRINT: a Cas13a-based platform for detection of small molecules | journal = Nucleic Acids Research | volume = 48 | issue = 17 | pages = e101 | date = September 2020 | pmid = 32797156 | pmc = 7515716 | doi = 10.1093/nar/gkaa673 | doi-access = free }}</ref> |
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In 2021, Dr. Hui Yang characterized novel miniature Cas13 protein (mCas13) variants, Cas13X and Cas13Y. Using a small portion of N gene sequence from SARS-CoV-2 as a target in characterization of mCas13, revealed the sensitivity and specificity of mCas13 coupled with RT-LAMP for detection of SARS-CoV-2 in both synthetic and clinical samples over other available standard tests like RT-qPCR (1 copy/μL).<ref>{{cite journal | vauthors = Mahas A, Wang Q, Marsic T, Mahfouz MM | title = A Novel Miniature CRISPR-Cas13 System for SARS-CoV-2 Diagnostics | journal = ACS Synthetic Biology | volume = 10 | issue = 10 | pages = 2541–2551 | date = October 2021 | pmid = 34546709 | pmc = 8482783 | doi = 10.1021/acssynbio.1c00181 }}</ref> |
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These differences may give Cpf1 some advantages over Cas9. For example, Cpf1's small crRNAs are ideal for multiplexed genome editing, as more of them can be packaged in one vector than can Cas9's sgRNAs. As well, the sticky 5' overhangs left by Cpf1 can be used for DNA assembly that is much more target-specific than traditional Restriction Enzyme cloning.<ref name="PMC5316869">{{cite journal | vauthors = Kim H, Kim ST, Ryu J, Kang BC, Kim JS, and Kim SG | title = CRISPR/Cpf1-mediated DNA-free plant genome editing | journal = Nature Communications | volume = 8 | issue = 14406 | pages = 14406 | date = February 2017 | pmc = 5316869 | doi = 10.1038/ncomms14406 | pmid=28205546}}</ref> Finally, Cpf1 cleaves DNA 18-23 bp downstream from the PAM site. This means there is no disruption to the recognition sequence after repair, and so Cpf1 enables multiple rounds of DNA cleavage. By contrast, since Cas9 cuts only 3 bp upstream of the PAM site, the NHEJ pathway results in indel mutations which destroy the recognition sequence, thereby preventing further rounds of cutting. In theory, repeated rounds of DNA cleavage should cause an increased opportunity for the desired genomic editing to occur.<ref>{{cite web|title = Cpf1 Nuclease|url = https://www.abmgood.com/marketing/knowledge_base/CRISPR_Cas9_Introduction_Part7.php#ATSPC|website = abmgood.com|accessdate = 2017-12-14}}</ref> |
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== Locus structure == |
== Locus structure == |
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=== Repeats and spacers === |
=== Repeats and spacers === |
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The CRISPR array is made up of an AT-rich leader sequence followed by short repeats that are separated by unique spacers.<ref name="Hille2016">{{cite journal | vauthors = Hille F, Charpentier E | title = CRISPR-Cas: biology, mechanisms and relevance | journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume = 371 | issue = 1707 | date = November 2016 | pmid = 27672148 | pmc = 5052741 | doi = 10.1098/rstb.2015.0496 | page=20150496}}</ref> CRISPR repeats typically range in size from 28 to 37 [[base pair]]s (bps), though there can be as few as 23 bp and as many as 55 bp.<ref name="Barrangou2014">{{cite journal | vauthors = Barrangou R, Marraffini LA | author-link1=Rodolphe Barrangou | title = CRISPR-Cas systems: Prokaryotes upgrade to adaptive immunity | journal = Molecular Cell | volume = 54 | issue = 2 | pages = 234–244 | date = April 2014 | pmid = 24766887 | pmc = 4025954 | doi = 10.1016/j.molcel.2014.03.011 }}</ref> Some show [[dyad symmetry]], implying the formation of a [[nucleic acid secondary structure|secondary structure]] such as a [[stem-loop]] ('hairpin') in the RNA, while others are designed to be unstructured. The size of spacers in different CRISPR arrays is typically 32 to 38 bp (range 21 to 72 bp).<ref name="Barrangou2014"/> New spacers can appear rapidly as part of the immune response to phage infection.<ref name="pmid17894817"/> There are usually fewer than 50 units of the repeat-spacer sequence in a CRISPR array.<ref name="Barrangou2014"/> |
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=== CRISPR RNA structures === |
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The CRISPR array comprises an AT-rich leader sequence followed by short repeats that are separated by unique spacers.<ref name="Hille2016">{{cite journal | vauthors = Hille F, Charpentier E | title = CRISPR-Cas: biology, mechanisms and relevance | journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume = 371 | issue = 1707 | date = November 2016 | pmid = 27672148 | pmc = 5052741 | doi = 10.1098/rstb.2015.0496 | pages=20150496}}</ref> CRISPR repeats typically range in size from 28 to 37 [[base pairs]] (bps), though there can be as few as 23 bp and as many as 55 bp.<ref name="Barrangou2014">{{cite journal | vauthors = Barrangou R, Marraffini LA | title = CRISPR-Cas systems: Prokaryotes upgrade to adaptive immunity | journal = Molecular Cell | volume = 54 | issue = 2 | pages = 234–44 | date = April 2014 | pmid = 24766887 | pmc = 4025954 | doi = 10.1016/j.molcel.2014.03.011 }}</ref> Some show [[dyad symmetry]], implying the formation of a [[nucleic acid secondary structure|secondary structure]] such as a [[stem-loop]] ('hairpin') in the RNA, while others are predicted to be unstructured. The size of spacers in different CRISPR arrays is typically 32 to 38 bp (range 21 to 72 bp).<ref name="Barrangou2014" /> New spacers can appear rapidly as part of the immune response to phage infection.<ref name="pmid17894817" /> There are usually fewer than 50 units of the repeat-spacer sequence in a CRISPR array.<ref name="Barrangou2014" /> |
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<gallery title="Gallery of secondary structure images" perrow="5"> |
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Image:RF01315.png| CRISPR-DR2: Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF01315 RF01315]. |
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Image:RF01318.png| CRISPR-DR5: Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF01318 RF011318]. |
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Image:RF01319.png| CRISPR-DR6: Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF01319 RF01319]. |
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Image:RF01321.png| CRISPR-DR8: Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF01321 RF01321]. |
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Image:RF01322.png| CRISPR-DR9: Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF01322 RF01322]. |
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Image:RF01332.png| CRISPR-DR19: Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF01332 RF01332]. |
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Image:RF01350.png| CRISPR-DR41: Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF01350 RF01350]. |
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Image:RF01365.png| CRISPR-DR52: Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF01365 RF01365]. |
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Image:RF01370.png| CRISPR-DR57: Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF01370 RF01370]. |
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Image:RF01378.png| CRISPR-DR65: Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF01378 RF01378]. |
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</gallery> |
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=== Cas genes and CRISPR subtypes === |
=== Cas genes and CRISPR subtypes === |
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Small clusters of ''cas'' genes are often located next to CRISPR repeat-spacer arrays. Collectively the 93 ''cas'' genes are grouped into 35 families based on sequence similarity of the encoded proteins. 11 of the 35 families form the ''cas'' core, which includes the protein families Cas1 through Cas9. A complete CRISPR-Cas locus has at least one gene belonging to the ''cas'' core.<!-- The numbers are from Makarova2015, and the Makarova2018 source has expanded them a bit. Its fig1 mentions 13 core gene families (instead of 11), but there's no mention of total gene families nor total gene count. --><ref name="Makarova2018">{{cite journal | vauthors = Koonin EV, Makarova KS | title = Origins and evolution of CRISPR-Cas systems | journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume = 374 | issue = 1772 | page = 20180087 | date = May 2019 | pmid = 30905284 | pmc = 6452270 | doi = 10.1098/rstb.2018.0087 | doi-access = free }}</ref> |
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CRISPR-Cas systems fall into two classes. Class 1 systems use a complex of multiple Cas proteins to degrade foreign nucleic acids. Class 2 systems use a single large Cas protein for the same purpose. Class 1 is divided into types I, III, and IV; class 2 is divided into types II, V, and VI.<ref name="Wright2016">{{cite journal | vauthors = Wright AV, Nuñez JK, Doudna JA | author-link3=Jennifer Doudna | title = Biology and Applications of CRISPR Systems: Harnessing Nature's Toolbox for Genome Engineering | journal = Cell | volume = 164 | issue = 1–2 | pages = 29–44 | date = January 2016 | pmid = 26771484 | doi = 10.1016/j.cell.2015.12.035 | doi-access = free }}</ref> The 6 system types are divided into 33 subtypes.<ref name="Makarova2020">{{cite journal |vauthors=Makarova KS, Wolf YI, Iranzo J, Shmakov SA, Alkhnbashi OS, Brouns SJ, Charpentier E, Cheng D, Haft DH, Horvath P, Moineau S, Mojica FJ, Scott D, Shah SA, Siksnys V, Terns MP, Venclovas Č, White MF, Yakunin AF, Yan W, Zhang F, Garrett RA, Backofen R, van der Oost J, Barrangou R, Koonin EV | title = Evolutionary classification of CRISPR–Cas systems: a burst of class 2 and derived variants | journal = Nature Reviews Microbiology | date = December 2019 | volume = 18 | issue = 1 |pages = 67–83 | doi = 10.1038/s41579-019-0299-x | doi-access = free | pmid = 31857715 | pmc = 8905525 | hdl = 10045/102627 | hdl-access = free }}</ref> Each type and most subtypes are characterized by a "signature gene" found almost exclusively in the category. Classification is also based on the complement of ''cas'' genes that are present. Most CRISPR-Cas systems have a Cas1 protein. The [[phylogeny]] of Cas1 proteins generally agrees with the classification system,<ref name="Makarova2015">{{cite journal | vauthors = Makarova KS, Wolf YI, Alkhnbashi OS, Costa F, Shah SA, Saunders SJ, Barrangou R, Brouns SJ, Charpentier E, Haft DH, Horvath P, Moineau S, Mojica FJ, Terns RM, Terns MP, White MF, Yakunin AF, Garrett RA, van der Oost J, Backofen R, Koonin EV | author-link7=Rodolphe Barrangou | author-link21=Eugene Koonin | title = An updated evolutionary classification of CRISPR-Cas systems | journal = Nature Reviews. Microbiology | volume = 13 | issue = 11 | pages = 722–736 | date = November 2015 | pmid = 26411297 | pmc = 5426118 | doi = 10.1038/nrmicro3569 }}</ref> but exceptions exist due to module shuffling.<ref name="Makarova2018"/> Many organisms contain multiple CRISPR-Cas systems suggesting that they are compatible and may share components.<ref name="pmid22337052">{{cite journal | vauthors = Wiedenheft B, Sternberg SH, Doudna JA | author-link3=Jennifer Doudna | title = RNA-guided genetic silencing systems in bacteria and archaea | journal = Nature | volume = 482 | issue = 7385 | pages = 331–338 | date = February 2012 | pmid = 22337052 | doi = 10.1038/nature10886 | bibcode = 2012Natur.482..331W }}</ref><ref name="pmid23320564">{{cite journal | vauthors = Deng L, Garrett RA, Shah SA, Peng X, She Q | title = A novel interference mechanism by a type IIIB CRISPR-Cmr module in Sulfolobus | journal = Molecular Microbiology | volume = 87 | issue = 5 | pages = 1088–1099 | date = March 2013 | pmid = 23320564 | doi = 10.1111/mmi.12152 | doi-access = }}</ref> The sporadic distribution of the CRISPR-Cas subtypes suggests that the CRISPR-Cas system is subject to [[horizontal gene transfer]] during microbial [[evolution]]. |
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Small clusters of ''cas'' genes are often located next to CRISPR repeat-spacer arrays. Collectively there are 93 ''cas'' genes that are grouped into 35 families based on sequence similarity of the encoded proteins. 11 of the 35 families form the ''cas'' core, which includes the protein families Cas1 through Cas9. A complete CRISPR-Cas locus has at least one gene belonging to the ''cas'' core.<ref name="Makarova2015" /> |
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CRISPR-Cas systems fall into two classes. Class 1 systems use a complex of multiple Cas proteins to degrade foreign nucleic acids. Class 2 systems use a single large Cas protein for the same purpose. Class 1 is divided into types I, III, and IV; class 2 is divided into types II, V, and VI.<ref name="Wright2016">{{cite journal | vauthors = Wright AV, Nuñez JK, Doudna JA | title = Biology and Applications of CRISPR Systems: Harnessing Nature's Toolbox for Genome Engineering | journal = Cell | volume = 164 | issue = 1–2 | pages = 29–44 | date = January 2016 | pmid = 26771484 | doi = 10.1016/j.cell.2015.12.035 }}</ref> The 6 system types are divided into 19 subtypes.<ref name="Westra2016">{{cite journal | last1 = Westra | first1 = Edze R. | last2 = Dowling | first2 = Andrea J. | last3 = Broniewski | first3 = Jenny M. | last4 = van Houte | first4 = Stineke | name-list-format = vanc | title = Evolution and Ecology of CRISPR | journal = Annual Review of Ecology, Evolution, and Systematics | date = November 2016 | volume = 47 | issue = 1 |pages = 307–331 | doi = 10.1146/annurev-ecolsys-121415-032428 }}</ref> Each type and most subtypes are characterized by a "signature gene" found almost exclusively in the category. Classification is also based on the complement of ''cas'' genes that are present. Most CRISPR-Cas systems have a Cas1 protein. The [[phylogeny]] of Cas1 proteins generally agrees with the classification system.<ref name="Makarova2015">{{cite journal | vauthors = Makarova KS, Wolf YI, Alkhnbashi OS, Costa F, Shah SA, Saunders SJ, Barrangou R, Brouns SJ, Charpentier E, Haft DH, Horvath P, Moineau S, Mojica FJ, Terns RM, Terns MP, White MF, Yakunin AF, Garrett RA, van der Oost J, Backofen R, Koonin EV | display-authors = 6 | title = An updated evolutionary classification of CRISPR-Cas systems | journal = Nature Reviews. Microbiology | volume = 13 | issue = 11 | pages = 722–36 | date = November 2015 | pmid = 26411297 | pmc = 5426118 | doi = 10.1038/nrmicro3569 }}</ref> Many organisms contain multiple CRISPR-Cas systems suggesting that they are compatible and may share components.<ref name="pmid22337052">{{cite journal | vauthors = Wiedenheft B, Sternberg SH, Doudna JA | title = RNA-guided genetic silencing systems in bacteria and archaea | journal = Nature | volume = 482 | issue = 7385 | pages = 331–8 | date = February 2012 | pmid = 22337052 | doi = 10.1038/nature10886 | bibcode = 2012Natur.482..331W }}</ref><ref name="pmid23320564">{{cite journal | vauthors = Deng L, Garrett RA, Shah SA, Peng X, She Q | title = A novel interference mechanism by a type IIIB CRISPR-Cmr module in Sulfolobus | journal = Molecular Microbiology | volume = 87 | issue = 5 | pages = 1088–99 | date = March 2013 | pmid = 23320564 | doi = 10.1111/mmi.12152 | doi-access = free }}</ref> The sporadic distribution of the CRISPR/Cas subtypes suggests that the CRISPR/Cas system is subject to [[horizontal gene transfer]] during microbial [[evolution]]. |
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{{missing information|table|UniProt and InterPro cross-reference|date=October 2020}} |
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{| class="wikitable" |
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{| class="wikitable center" style="width:100%" |
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|+ Signature genes and their putative functions for the major and minor CRISPR-cas types. |
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|+ Signature genes and their putative functions for the major and minor CRISPR-cas types |
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! Class !! Cas type !! Signature protein !! Function !! Reference |
! Class !! Cas type |
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!Cas subtype!! Signature protein !! Function !! Reference |
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| rowspan="19" | 1 || rowspan="8" | I |
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| 1 || I || Cas3 || Single-stranded DNA nuclease (HD domain) and ATP-dependent helicase ||<ref name="pmid21343909">{{cite journal | vauthors = Sinkunas T, Gasiunas G, Fremaux C, Barrangou R, Horvath P, Siksnys V | title = Cas3 is a single-stranded DNA nuclease and ATP-dependent helicase in the CRISPR/Cas immune system | journal = The EMBO Journal | volume = 30 | issue = 7 | pages = 1335–42 | date = April 2011 | pmid = 21343909 | pmc = 3094125 | doi = 10.1038/emboj.2011.41 }}</ref><ref name="ReferenceB">{{cite journal | vauthors = Huo Y, Nam KH, Ding F, Lee H, Wu L, Xiao Y, Farchione MD, Zhou S, Rajashankar K, Kurinov I, Zhang R, Ke A | title = Structures of CRISPR Cas3 offer mechanistic insights into Cascade-activated DNA unwinding and degradation | journal = Nature Structural & Molecular Biology | volume = 21 | issue = 9 | pages = 771–7 | date = September 2014 | pmid = 25132177 | pmc = 4156918 | doi = 10.1038/nsmb.2875 }}</ref> |
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| {{sdash}} ||[[Cas3]] || Single-stranded DNA nuclease (HD domain) and ATP-dependent helicase ||<ref name="pmid21343909">{{cite journal | vauthors = Sinkunas T, Gasiunas G, Fremaux C, Barrangou R, Horvath P, Siksnys V | author-link4=Rodolphe Barrangou | title = Cas3 is a single-stranded DNA nuclease and ATP-dependent helicase in the CRISPR/Cas immune system | journal = The EMBO Journal | volume = 30 | issue = 7 | pages = 1335–1342 | date = April 2011 | pmid = 21343909 | pmc = 3094125 | doi = 10.1038/emboj.2011.41 }}</ref><ref name="ReferenceB">{{cite journal | vauthors = Huo Y, Nam KH, Ding F, Lee H, Wu L, Xiao Y, Farchione MD, Zhou S, Rajashankar K, Kurinov I, Zhang R, Ke A | title = Structures of CRISPR Cas3 offer mechanistic insights into Cascade-activated DNA unwinding and degradation | journal = Nature Structural & Molecular Biology | volume = 21 | issue = 9 | pages = 771–777 | date = September 2014 | pmid = 25132177 | pmc = 4156918 | doi = 10.1038/nsmb.2875 }}</ref> |
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|{{nowrap|I-A}}|| Cas8a, Cas5 || rowspan="3" | Cas8 is a Subunit of the interference module that is important in targeting of invading DNA by recognizing the [[Protospacer adjacent motif|PAM]] sequence. Cas5 is required for processing and stability of crRNAs. || rowspan="3" |<ref name="Makarova2015"/><ref>{{cite journal | vauthors = Brendel J, Stoll B, Lange SJ, Sharma K, Lenz C, Stachler AE, Maier LK, Richter H, Nickel L, Schmitz RA, Randau L, Allers T, Urlaub H, Backofen R, Marchfelder A | title = A complex of Cas proteins 5, 6, and 7 is required for the biogenesis and stability of clustered regularly interspaced short palindromic repeats (crispr)-derived rnas (crrnas) in Haloferax volcanii | journal = The Journal of Biological Chemistry | volume = 289 | issue = 10 | pages = 7164–77 | date = March 2014 | pmid = 24459147 | doi = 10.1074/jbc.M113.508184 | pmc = 3945376 | doi-access = free }}</ref> |
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|{{nowrap|I-B}}|| Cas8b |
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|{{nowrap|I-C}}|| Cas8c |
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|{{nowrap|I-D}}|| Cas10d || rowspan="2" | contains a domain homologous to the palm domain of nucleic acid polymerases and nucleotide cyclases || rowspan="2" |<ref name="pmid24728998">{{cite journal | vauthors = Chylinski K, Makarova KS, Charpentier E, Koonin EV | author-link4=Eugene Koonin | title = Classification and evolution of type II CRISPR-Cas systems | journal = Nucleic Acids Research | volume = 42 | issue = 10 | pages = 6091–6105 | date = June 2014 | pmid = 24728998 | pmc = 4041416 | doi = 10.1093/nar/gku241 }}</ref><ref name="pmid21756346">{{cite journal | vauthors = Makarova KS, Aravind L, Wolf YI, Koonin EV | author-link4=Eugene Koonin | title = Unification of Cas protein families and a simple scenario for the origin and evolution of CRISPR-Cas systems | journal = Biology Direct | volume = 6 | page = 38 | date = July 2011 | pmid = 21756346 | pmc = 3150331 | doi = 10.1186/1745-6150-6-38 | doi-access=free }}</ref> |
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|{{nowrap|I-E}}|| Cse1, Cse2 |
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|{{nowrap|I-F}}|| Csy1, Csy2, Csy3 || Type IF-3 have been implicated in [[CRISPR-associated transposons]]||<ref name="Makarova2015"/> |
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|{{nowrap|I-G}}{{#tag:ref | Subtype {{nowrap|I-G}} was previously known as subtype {{nowrap|I-U}}.<ref name="Makarova2015"/> | group = Note | name = {{nowrap|I-U}} }}|| GSU0054 || ||<ref name="Makarova2019">{{cite journal | vauthors = Makarova KS, Wolf YI, Iranzo J, Shmakov SA, Alkhnbashi OS, Brouns SJ, Charpentier E, Cheng D, Haft DH, Horvath P, Moineau S, Mojica FJ, Scott D, Shah SA, Siksnys V, Terns MP, Venclovas Č, White MF, Yakunin AF, Yan W, Zhang F, Garrett RA, Backofen R, van der Oost J, Barrangou R, Koonin EV | title = Evolutionary classification of CRISPR-Cas systems: a burst of class 2 and derived variants | journal = Nature Reviews. Microbiology | volume = 18 | issue = 2 | pages = 67–83 | date = February 2020 | pmid = 31857715 | doi = 10.1038/s41579-019-0299-x | pmc = 8905525 | hdl-access = free | hdl = 10045/102627 }}</ref> |
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| || IU || GSU0054 || ||<ref name="Makarova2015" /> |
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| rowspan="7" | III |
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| || III || Cas10 || [[Homology (chemistry)|Homolog]] of Cas10d and Cse1 ||<ref name="pmid21756346" /> |
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| {{sdash}} || Cas10 || [[Homologous series|Homolog]] of Cas10d and Cse1. Binds CRISPR target RNA and promotes stability of the interference complex ||<ref name="pmid21756346"/><ref name="pmid30840895">{{cite journal | vauthors = Mogila I, Kazlauskiene M, Valinskyte S, Tamulaitiene G, Tamulaitis G, Siksnys V | title = Genetic Dissection of the Type {{nowrap|III-A}} CRISPR-Cas System Csm Complex Reveals Roles of Individual Subunits | journal = Cell Reports | volume = 26 | issue = 10 | pages = 2753–2765.e4 | date = March 2019 | pmid = 30840895 | doi = 10.1016/j.celrep.2019.02.029 | doi-access = free }}</ref> |
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|{{nowrap|III-A}}|| Csm2 || Not determined ||<ref name="Makarova2015"/> |
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|{{nowrap|III-B}}|| Cmr5 || Not determined ||<ref name="Makarova2015"/> |
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|{{nowrap|III-C}}|| Cas10 or Csx11 || ||<ref name="Makarova2015"/><ref name="pmid30840895"/> |
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|{{nowrap|III-D}}|| Csx10 || ||<ref name="Makarova2015"/> |
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|{{nowrap|III-E}}|| || ||<ref name="Makarova2019"/> |
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| || IV || Csf1 || || |
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|{{nowrap|III-F}}|| || ||<ref name="Makarova2019"/> |
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| || IVA || || || |
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| rowspan="4" | IV |
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| {{sdash}} || Csf1 || ||<ref name="Makarova2019"/> |
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|{{nowrap|IV-A}}|| || ||<ref name="Makarova2019"/> |
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| 2 || II || [[Cas9]] || [[Nuclease]]s RuvC and HNH together produce [[double-strand breaks|DSBs]], and separately can produce single-strand breaks. Ensures the acquisition of functional spacers during adaptation. ||<ref name="pmid22949671">{{cite journal | vauthors = Gasiunas G, Barrangou R, Horvath P, Siksnys V | title = Cas9-crRNA ribonucleoprotein complex mediates specific DNA cleavage for adaptive immunity in bacteria | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 109 | issue = 39 | pages = E2579–86 | date = September 2012 | pmid = 22949671 | pmc = 3465414 | doi = 10.1073/pnas.1208507109 | bibcode = 2012PNAS..109E2579G }}</ref><ref>{{cite journal | vauthors = Heler R, Samai P, Modell JW, Weiner C, Goldberg GW, Bikard D, Marraffini LA | title = Cas9 specifies functional viral targets during CRISPR-Cas adaptation | journal = Nature | volume = 519 | issue = 7542 | pages = 199–202 | date = March 2015 | pmid = 25707807 | pmc = 4385744 | doi = 10.1038/nature14245 | bibcode = 2015Natur.519..199H }}</ref> |
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|{{nowrap|IV-B}}|| || ||<ref name="Makarova2019"/> |
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| || IIA || Csn2 || Ring-shaped DNA-binding protein. Involved in primed adaptation in Type II CRISPR system. ||<ref>{{cite journal | vauthors = Nam KH, Kurinov I, Ke A | title = Crystal structure of clustered regularly interspaced short palindromic repeats (CRISPR)-associated Csn2 protein revealed Ca2+-dependent double-stranded DNA binding activity | journal = The Journal of Biological Chemistry | volume = 286 | issue = 35 | pages = 30759–68 | date = September 2011 | pmid = 21697083 | pmc = 3162437 | doi = 10.1074/jbc.M111.256263 }}</ref> |
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|{{nowrap|IV-C}}|| || ||<ref name="Makarova2019"/> |
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| || IIB || Cas4 || Not Determined || |
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| rowspan="23" | 2 || rowspan="4" | II |
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| ||IIC || || Characterized by the absence of either Csn2 or Cas4 ||<ref name="pmid23563642">{{cite journal | vauthors = Chylinski K, Le Rhun A, Charpentier E | title = The tracrRNA and Cas9 families of type II CRISPR-Cas immunity systems | journal = RNA Biology | volume = 10 | issue = 5 | pages = 726–37 | date = May 2013 | pmid = 23563642 | pmc = 3737331 | doi = 10.4161/rna.24321 }}</ref> |
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| {{sdash}} ||[[Cas9]] || [[Nuclease]]s RuvC and HNH together produce [[double-strand breaks|DSBs]], and separately can produce single-strand breaks. Ensures the acquisition of functional spacers during adaptation. ||<ref name="pmid22949671">{{cite journal | vauthors = Gasiunas G, Barrangou R, Horvath P, Siksnys V | author-link2=Rodolphe Barrangou | title = Cas9-crRNA ribonucleoprotein complex mediates specific DNA cleavage for adaptive immunity in bacteria | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 109 | issue = 39 | pages = E2579–2586 | date = September 2012 | pmid = 22949671 | pmc = 3465414 | doi = 10.1073/pnas.1208507109 | bibcode = 2012PNAS..109E2579G | doi-access=free }}</ref><ref>{{cite journal | vauthors = Heler R, Samai P, Modell JW, Weiner C, Goldberg GW, Bikard D, Marraffini LA | title = Cas9 specifies functional viral targets during CRISPR-Cas adaptation | journal = Nature | volume = 519 | issue = 7542 | pages = 199–202 | date = March 2015 | pmid = 25707807 | pmc = 4385744 | doi = 10.1038/nature14245 | bibcode = 2015Natur.519..199H }}</ref> |
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|{{nowrap|II-A}}|| Csn2 || Ring-shaped DNA-binding protein. Involved in primed adaptation in Type II CRISPR system. ||<ref>{{cite journal | vauthors = Nam KH, Kurinov I, Ke A | title = Crystal structure of clustered regularly interspaced short palindromic repeats (CRISPR)-associated Csn2 protein revealed Ca2+-dependent double-stranded DNA binding activity | journal = The Journal of Biological Chemistry | volume = 286 | issue = 35 | pages = 30759–30768 | date = September 2011 | pmid = 21697083 | pmc = 3162437 | doi = 10.1074/jbc.M111.256263 | doi-access = free }}</ref> |
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| || V || Cpf1, C2c1, C2c3 || Nuclease RuvC. Lacks HNH. ||<ref name="Wright2016" /> |
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|{{nowrap|II-B}}||[[Cas4]] || Endonuclease that works with cas1 and cas2 to generate spacer sequences || <ref>{{cite journal | vauthors = Lee H, Dhingra Y, Sashital DG | title = The Cas4-Cas1-Cas2 complex mediates precise prespacer processing during CRISPR adaptation | journal = eLife | volume = 8 | date = April 2019 | pmid = 31021314 | doi = 10.7554/eLife.44248 | pmc = 6519985 | doi-access = free }}</ref> |
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|{{nowrap|II-C}}|| || Characterized by the absence of either Csn2 or Cas4 ||<ref name="pmid23563642">{{cite journal | vauthors = Chylinski K, Le Rhun A, Charpentier E | title = The tracrRNA and Cas9 families of type II CRISPR-Cas immunity systems | journal = RNA Biology | volume = 10 | issue = 5 | pages = 726–737 | date = May 2013 | pmid = 23563642 | pmc = 3737331 | doi = 10.4161/rna.24321 }}</ref> |
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| rowspan="12" | V |
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| {{sdash}} || Cas12 || Nuclease RuvC. Lacks HNH. ||<ref name="Wright2016"/><ref>{{cite journal | vauthors = Makarova KS, Zhang F, Koonin EV | title = SnapShot: Class 2 CRISPR-Cas Systems | journal = Cell | volume = 168 | issue = 1–2 | pages = 328–328.e1 | date = January 2017 | pmid = 28086097 | doi = 10.1016/j.cell.2016.12.038 | doi-access = free }}</ref> |
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|{{nowrap|V-A}}|| [[Cas12a]] (Cpf1) || Auto-processing pre-crRNA activity for multiplex gene regulation||<ref name="Makarova2019"/><ref>{{cite journal | vauthors = Paul B, Montoya G | title = CRISPR-Cas12a: Functional overview and applications | journal = Biomedical Journal | volume = 43 | issue = 1 | pages = 8–17 | date = February 2020 | pmid = 32200959 | pmc = 7090318 | doi = 10.1016/j.bj.2019.10.005 }}</ref> |
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|{{nowrap|V-B}}|| Cas12b (C2c1) || ||<ref name="Makarova2019"/> |
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|{{nowrap|V-C}}|| Cas12c (C2c3) || ||<ref name="Makarova2019"/> |
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|{{nowrap|V-D}}|| Cas12d (CasY) || ||<ref name="Makarova2019"/> |
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|{{nowrap|V-E}}|| Cas12e (CasX) || ||<ref name="Makarova2019"/> |
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|{{nowrap|V-F}}|| Cas12f (Cas14, C2c10) || ||<ref name="Makarova2019"/> |
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|{{nowrap|V-G}}|| Cas12g || ||<ref name="Makarova2019"/> |
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|{{nowrap|V-H}}|| Cas12h || ||<ref name="Makarova2019"/> |
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|{{nowrap|V-I}}|| Cas12i || ||<ref name="Makarova2019"/> |
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|{{nowrap|V-K}}{{#tag:ref | Subtype {{nowrap|V-K}} was previously known as subtype {{nowrap|V-U}}5.<ref name="Makarova2019"/> | group = Note | name = {{nowrap|V-U}}5 }}|| Cas12k (C2c5) || Type V-K have been implicated in [[CRISPR-associated transposons]].||<ref name="Makarova2019"/> |
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|{{nowrap|V-U}}|| C2c4, C2c8, C2c9 || ||<ref name="Makarova2019"/> |
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| rowspan="7" | VI |
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| {{sdash}} || Cas13 || RNA-guided RNase || <ref name="Wright2016"/><ref>{{cite journal | vauthors = Cox DB, Gootenberg JS, Abudayyeh OO, Franklin B, Kellner MJ, Joung J, Zhang F | author-link7=Feng Zhang | title = RNA editing with CRISPR-Cas13 | journal = Science | volume = 358 | issue = 6366 | pages = 1019–1027 | date = November 2017 | pmid = 29070703 | pmc = 5793859 | doi = 10.1126/science.aaq0180 | bibcode = 2017Sci...358.1019C }}</ref> |
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|{{nowrap|VI-A}}|| Cas13a (C2c2) || ||<ref name="Makarova2019"/> |
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|{{nowrap|VI-B}}|| Cas13b || ||<ref name="Makarova2019"/> |
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|{{nowrap|VI-C}}|| Cas13c || ||<ref name="Makarova2019"/> |
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|{{nowrap|VI-D}}|| Cas13d || ||<ref name="Makarova2019"/> |
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|VI-X |
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|Cas13x.1 |
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|RNA dependent RNA polymerase, Prophylactic RNA-virus inhibition |
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|<ref name="Xu-2021">{{cite journal | vauthors = Xu C, Zhou Y, Xiao Q, He B, Geng G, Wang Z, Cao B, Dong X, Bai W, Wang Y, Wang X, Zhou D, Yuan T, Huo X, Lai J, Yang H | title = Programmable RNA editing with compact CRISPR-Cas13 systems from uncultivated microbes | journal = Nature Methods | volume = 18 | issue = 5 | pages = 499–506 | date = May 2021 | pmid = 33941935 | doi = 10.1038/s41592-021-01124-4 | doi-access = free }}</ref> |
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|VI-Y |
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|<ref name="Xu-2021"/> |
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{{Clear}} |
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== Mechanism == |
== Mechanism == |
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[[File:The Stages of CRISPR immunity.svg|thumb|The stages of CRISPR immunity for each of the three major types of adaptive immunity.<br/> (1) Acquisition begins by recognition of invading DNA by [[Cas1]] and Cas2 and cleavage of a protospacer.<br/> (2) The protospacer is ligated to the direct repeat adjacent to the leader sequence and <br/>(3) single strand extension repairs the CRISPR and duplicates the direct repeat. The crRNA processing and interference stages occur differently in each of the three major CRISPR systems.<br/> (4) The primary CRISPR transcript is cleaved by cas genes to produce crRNAs.<br/> (5) In type I systems Cas6e/Cas6f cleave at the junction of ssRNA and dsRNA formed by hairpin loops in the direct repeat. Type II systems use a trans-activating (tracr) RNA to form dsRNA, which is cleaved by [[Cas9]] and RNaseIII. Type III systems use a Cas6 homolog that does not require hairpin loops in the direct repeat for cleavage.<br/> (6) In type II and type III systems secondary trimming is performed at either the 5' or 3' end to produce mature crRNAs.<br/> (7) Mature crRNAs associate with Cas proteins to form interference complexes.<br/> (8) In type I and type II systems, interactions between the protein and PAM sequence are required for degradation of invading DNA. Type III systems do not require a PAM for successful degradation and in type III-A systems basepairing occurs between the crRNA and mRNA rather than the DNA, targeted by type III-B systems.]] |
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[[File:12 Hegasy Cas9 Immun Wiki E CCBYSA.png|thumb|The CRISPR genetic locus provides bacteria with a defense mechanism to protect them from repeated phage infections.]] |
[[File:12 Hegasy Cas9 Immun Wiki E CCBYSA.png|thumb|The CRISPR genetic locus provides bacteria with a defense mechanism to protect them from repeated phage infections.]] |
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[[File:13 Hegasy CRISPR pre crRNA Wiki E CCBYSA.png|thumb|Transcripts of the CRISPR Genetic Locus and Maturation of pre-crRNA]] |
[[File:13 Hegasy CRISPR pre crRNA Wiki E CCBYSA.png|thumb|Transcripts of the CRISPR Genetic Locus and Maturation of pre-crRNA]] |
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[[File:14 Hegasy Cas9 3D Complex Wiki E CCBYSA.png|thumb|3D Structure of the CRISPR-Cas9 Interference Complex]] |
[[File:14 Hegasy Cas9 3D Complex Wiki E CCBYSA.png|thumb|3D Structure of the CRISPR-Cas9 Interference Complex]] |
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[[File:15 Hegasy Cas9 DNA Tool Wiki E CCBYSA.png|thumb|CRISPR-Cas9 as a Molecular Tool Introduces Targeted Double Strand DNA Breaks.]] |
[[File:15 Hegasy Cas9 DNA Tool Wiki E CCBYSA.png|thumb|CRISPR-Cas9 as a Molecular Tool Introduces Targeted Double Strand DNA Breaks.]] |
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[[File:16 Hegasy DNA Rep Wiki E CCBYSA.png|thumb|Double |
[[File:16 Hegasy DNA Rep Wiki E CCBYSA.png|thumb|Double-strand DNA breaks introduced by CRISPR-Cas9 allows further genetic manipulation by exploiting endogenous DNA repair mechanisms.]] |
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CRISPR-Cas immunity is a natural process of bacteria and archaea.<ref name="pmid33117331">{{cite journal | vauthors = Azangou-Khyavy M, Ghasemi M, Khanali J, Boroomand-Saboor M, Jamalkhah M, Soleimani M, Kiani J | title = CRISPR/Cas: From Tumor Gene Editing to T Cell-Based Immunotherapy of Cancer | journal = Frontiers in Immunology | volume = 11 | issue = | page = 2062 | date = 2020 | pmid = 33117331 | pmc = 7553049 | doi = 10.3389/fimmu.2020.02062 | doi-access = free }}</ref> CRISPR-Cas prevents bacteriophage infection, [[Bacterial conjugation|conjugation]] and [[transformation (genetics)#Natural transformation|natural transformation]] by degrading foreign nucleic acids that enter the cell.<ref name="Marraffini2015">{{cite journal | vauthors = Marraffini LA | title = CRISPR-Cas immunity in prokaryotes | journal = Nature | volume = 526 | issue = 7571 | pages = 55–61 | date = October 2015 | pmid = 26432244 | doi = 10.1038/nature15386 | bibcode = 2015Natur.526...55M }}</ref> |
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[[File:The Stages of CRISPR immunity.svg|frame|The stages of CRISPR immunity for each of the three major types of adaptive immunity. (1) Acquisition begins by recognition of invading DNA by [[Cas1]] and Cas2 and cleavage of a protospacer. (2) The protospacer is ligated to the direct repeat adjacent to the leader sequence and (3) single strand extension repairs the CRISPR and duplicates the direct repeat. The crRNA processing and interference stages occur differently in each of the three major CRISPR systems. (4) The primary CRISPR transcript is cleaved by cas genes to produce crRNAs. (5) In type I systems Cas6e/Cas6f cleave at the junction of ssRNA and dsRNA formed by hairpin loops in the direct repeat. Type II systems use a trans-activating (tracr) RNA to form dsRNA, which is cleaved by [[Cas9]] and RNaseIII. Type III systems use a Cas6 homolog that does not require hairpin loops in the direct repeat for cleavage. (6) In type II and type III systems secondary trimming is performed at either the 5’ or 3’ end to produce mature crRNAs. (7) Mature crRNAs associate with Cas proteins to form interference complexes. (8) In type I and type II systems, interactions between the protein and PAM sequence are required for degradation of invading DNA. Type III systems do not require a PAM for successful degradation and in type III-A systems basepairing occurs between the crRNA and mRNA rather than the DNA, targeted by type III-B systems.]] |
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CRISPR-Cas immunity is a natural process of bacteria and archaea. CRISPR-Cas prevents bacteriophage infection, [[conjugation (genetics)|conjugation]] and [[transformation (genetics)#Natural transformation|natural transformation]] by degrading foreign nucleic acids that enter the cell.<ref name="Marraffini2015">{{cite journal | vauthors = Marraffini LA | title = CRISPR-Cas immunity in prokaryotes | journal = Nature | volume = 526 | issue = 7571 | pages = 55–61 | date = October 2015 | pmid = 26432244 | doi = 10.1038/nature15386 }}</ref> |
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=== Spacer acquisition === |
=== Spacer acquisition === |
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When a [[microbe]] is invaded by a [[ |
When a [[microbe]] is invaded by a [[bacteriophage]], the first stage of the immune response is to capture phage DNA and insert it into a CRISPR locus in the form of a spacer. [[Cas1]] and [[Cas2]] are found in both types of CRISPR-Cas immune systems, which indicates that they are involved in spacer acquisition. Mutation studies confirmed this hypothesis, showing that removal of Cas1 or Cas2 stopped spacer acquisition, without affecting CRISPR immune response.<ref name="pmid19120484">{{cite journal | vauthors = Aliyari R, Ding SW | title = RNA-based viral immunity initiated by the Dicer family of host immune receptors | journal = Immunological Reviews | volume = 227 | issue = 1 | pages = 176–188 | date = January 2009 | pmid = 19120484 | pmc = 2676720 | doi = 10.1111/j.1600-065X.2008.00722.x }}</ref><ref name="pmid23696746">{{cite journal | vauthors = Dugar G, Herbig A, Förstner KU, Heidrich N, Reinhardt R, Nieselt K, Sharma CM | title = High-resolution transcriptome maps reveal strain-specific regulatory features of multiple Campylobacter jejuni isolates | journal = PLOS Genetics | volume = 9 | issue = 5 | pages = e1003495 | date = May 2013 | pmid = 23696746 | pmc = 3656092 | doi = 10.1371/journal.pgen.1003495 | doi-access = free }}</ref><ref name="pmid22160698">{{cite journal | vauthors = Hatoum-Aslan A, Maniv I, Marraffini LA | title = Mature clustered, regularly interspaced, short palindromic repeats RNA (crRNA) length is measured by a ruler mechanism anchored at the precursor processing site | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 108 | issue = 52 | pages = 21218–21222 | date = December 2011 | pmid = 22160698 | pmc = 3248500 | doi = 10.1073/pnas.1112832108 | bibcode = 2011PNAS..10821218H | doi-access = free }}</ref><ref name="pmid22402487">{{cite journal | vauthors = Yosef I, Goren MG, Qimron U | title = Proteins and DNA elements essential for the CRISPR adaptation process in ''Escherichia coli'' | journal = Nucleic Acids Research | volume = 40 | issue = 12 | pages = 5569–5576 | date = July 2012 | pmid = 22402487 | pmc = 3384332 | doi = 10.1093/nar/gks216 }}</ref><ref name="pmid22558257">{{cite journal | vauthors = Swarts DC, Mosterd C, van Passel MW, Brouns SJ | title = CRISPR interference directs strand specific spacer acquisition | journal = PLOS ONE | volume = 7 | issue = 4 | pages = e35888 | year = 2012 | pmid = 22558257 | pmc = 3338789 | doi = 10.1371/journal.pone.0035888 | bibcode = 2012PLoSO...735888S | doi-access = free }}</ref> |
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Multiple Cas1 proteins have been characterised and their structures resolved.<ref name="pmid21219465">{{cite journal | vauthors = Babu M, Beloglazova N, Flick R, Graham C, Skarina T, Nocek B, Gagarinova A, Pogoutse O, Brown G, Binkowski A, Phanse S, Joachimiak A, Koonin EV, Savchenko A, Emili A, Greenblatt J, Edwards AM, Yakunin AF | |
Multiple Cas1 proteins have been characterised and their structures resolved.<ref name="pmid21219465">{{cite journal | vauthors = Babu M, Beloglazova N, Flick R, Graham C, Skarina T, Nocek B, Gagarinova A, Pogoutse O, Brown G, Binkowski A, Phanse S, Joachimiak A, Koonin EV, Savchenko A, Emili A, Greenblatt J, Edwards AM, Yakunin AF | author-link=Eugene Koonin | title = A dual function of the CRISPR-Cas system in bacterial antivirus immunity and DNA repair | journal = Molecular Microbiology | volume = 79 | issue = 2 | pages = 484–502 | date = January 2011 | pmid = 21219465 | pmc = 3071548 | doi = 10.1111/j.1365-2958.2010.07465.x }}</ref><ref name="pmid19427858">{{cite journal | vauthors = Han D, Lehmann K, Krauss G | title = SSO1450—a CAS1 protein from Sulfolobus solfataricus P2 with high affinity for RNA and DNA | journal = FEBS Letters | volume = 583 | issue = 12 | pages = 1928–1932 | date = June 2009 | pmid = 19427858 | doi = 10.1016/j.febslet.2009.04.047 | doi-access = | bibcode = 2009FEBSL.583.1928H }}</ref><ref name="pmid19523907">{{cite journal | vauthors = Wiedenheft B, Zhou K, Jinek M, Coyle SM, Ma W, Doudna JA | author-link6=Jennifer Doudna | title = Structural basis for DNase activity of a conserved protein implicated in CRISPR-mediated genome defense | journal = Structure | volume = 17 | issue = 6 | pages = 904–912 | date = June 2009 | pmid = 19523907 | doi = 10.1016/j.str.2009.03.019 | doi-access = free }}</ref> Cas1 proteins have diverse [[amino acid]] sequences. However, their crystal structures are similar and all purified Cas1 proteins are metal-dependent nucleases/[[integrases]] that bind to DNA in a sequence-independent manner.<ref name="pmid22337052"/> Representative Cas2 proteins have been characterised and possess either (single strand) ssRNA-<ref name="pmid18482976">{{cite journal | vauthors = Beloglazova N, Brown G, Zimmerman MD, Proudfoot M, Makarova KS, Kudritska M, Kochinyan S, Wang S, Chruszcz M, Minor W, Koonin EV, Edwards AM, Savchenko A, Yakunin AF | author-link11=Eugene Koonin | title = A novel family of sequence-specific endoribonucleases associated with the clustered regularly interspaced short palindromic repeats | journal = The Journal of Biological Chemistry | volume = 283 | issue = 29 | pages = 20361–20371 | date = July 2008 | pmid = 18482976 | pmc = 2459268 | doi = 10.1074/jbc.M803225200 | doi-access=free }}</ref> or (double strand) dsDNA-<ref name="pmid21139194">{{cite journal | vauthors = Samai P, Smith P, Shuman S | title = Structure of a CRISPR-associated protein Cas2 from Desulfovibrio vulgaris | journal = Acta Crystallographica Section F | volume = 66 | issue = Pt 12 | pages = 1552–1556 | date = December 2010 | pmid = 21139194 | pmc = 2998353 | doi = 10.1107/S1744309110039801 }}</ref><ref name="pmid22942283">{{cite journal | vauthors = Nam KH, Ding F, Haitjema C, Huang Q, DeLisa MP, Ke A | title = Double-stranded endonuclease activity in Bacillus halodurans clustered regularly interspaced short palindromic repeats (CRISPR)-associated Cas2 protein | journal = The Journal of Biological Chemistry | volume = 287 | issue = 43 | pages = 35943–35952 | date = October 2012 | pmid = 22942283 | pmc = 3476262 | doi = 10.1074/jbc.M112.382598 | doi-access = free }}</ref> specific [[endoribonuclease]] activity. |
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In the I-E system of ''E. coli'' Cas1 and Cas2 form a complex where a Cas2 dimer bridges two Cas1 dimers.<ref name="pmid24793649">{{cite journal | vauthors = Nuñez JK, Kranzusch PJ, Noeske J, Wright AV, Davies CW, Doudna JA | title = Cas1-Cas2 complex formation mediates spacer acquisition during CRISPR-Cas adaptive immunity | journal = Nature Structural & Molecular Biology | volume = 21 | issue = 6 | pages = |
In the I-E system of ''E. coli'' Cas1 and Cas2 form a complex where a Cas2 dimer bridges two Cas1 dimers.<ref name="pmid24793649">{{cite journal | vauthors = Nuñez JK, Kranzusch PJ, Noeske J, Wright AV, Davies CW, Doudna JA | author-link6=Jennifer Doudna | title = Cas1-Cas2 complex formation mediates spacer acquisition during CRISPR-Cas adaptive immunity | journal = Nature Structural & Molecular Biology | volume = 21 | issue = 6 | pages = 528–534 | date = June 2014 | pmid = 24793649 | pmc = 4075942 | doi = 10.1038/nsmb.2820 }}</ref> In this complex Cas2 performs a non-enzymatic scaffolding role,<ref name="pmid24793649"/> binding double-stranded fragments of invading DNA, while Cas1 binds the single-stranded flanks of the DNA and catalyses their integration into CRISPR arrays.<ref name="pmid25707795">{{cite journal | vauthors = Nuñez JK, Lee AS, Engelman A, Doudna JA | author-link4=Jennifer Doudna | title = Integrase-mediated spacer acquisition during CRISPR-Cas adaptive immunity | journal = Nature | volume = 519 | issue = 7542 | pages = 193–198 | date = March 2015 | pmid = 25707795 | pmc = 4359072 | doi = 10.1038/nature14237 | bibcode = 2015Natur.519..193N }}</ref><ref name="pmid26478180">{{cite journal | vauthors = Wang J, Li J, Zhao H, Sheng G, Wang M, Yin M, Wang Y | title = Structural and Mechanistic Basis of PAM-Dependent Spacer Acquisition in CRISPR-Cas Systems | journal = Cell | volume = 163 | issue = 4 | pages = 840–853 | date = November 2015 | pmid = 26478180 | doi = 10.1016/j.cell.2015.10.008 | doi-access = free }}</ref><ref name="pmid26503043">{{cite journal | vauthors = Nuñez JK, Harrington LB, Kranzusch PJ, Engelman AN, Doudna JA | author-link5=Jennifer Doudna | title = Foreign DNA capture during CRISPR-Cas adaptive immunity | journal = Nature | volume = 527 | issue = 7579 | pages = 535–538 | date = November 2015 | pmid = 26503043 | pmc = 4662619 | doi = 10.1038/nature15760 | bibcode = 2015Natur.527..535N }}</ref> New spacers are usually added at the beginning of the CRISPR next to the leader sequence creating a chronological record of viral infections.<ref>{{cite journal | vauthors = Sorek R, Lawrence CM, Wiedenheft B | title = CRISPR-mediated adaptive immune systems in bacteria and archaea | journal = Annual Review of Biochemistry | volume = 82 | issue = 1 | pages = 237–266 | year = 2013 | pmid = 23495939 | doi = 10.1146/annurev-biochem-072911-172315 | doi-access = free }}</ref> In ''E. coli'' a [[Bacterial DNA binding protein|histone like protein]] called integration host factor ([[Bacterial DNA binding protein|IHF]]), which binds to the leader sequence, is responsible for the accuracy of this integration.<ref>{{cite journal | vauthors = Nuñez JK, Bai L, Harrington LB, Hinder TL, Doudna JA | author-link5=Jennifer Doudna | title = CRISPR Immunological Memory Requires a Host Factor for Specificity | journal = Molecular Cell | volume = 62 | issue = 6 | pages = 824–833 | date = June 2016 | pmid = 27211867 | doi = 10.1016/j.molcel.2016.04.027 | doi-access = free }}</ref> IHF also enhances integration efficiency in the type I-F system of ''[[Pectobacterium atrosepticum]]''.<ref>{{cite journal | vauthors = Fagerlund RD, Wilkinson ME, Klykov O, Barendregt A, Pearce FG, Kieper SN, Maxwell HW, Capolupo A, Heck AJ, Krause KL, Bostina M, Scheltema RA, Staals RH, Fineran PC | title = Spacer capture and integration by a type I-F Cas1-Cas2–3 CRISPR adaptation complex | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 114 | issue = 26 | pages = E5122–E5128 | date = June 2017 | pmid = 28611213 | pmc = 5495228 | doi = 10.1073/pnas.1618421114 | bibcode = 2017PNAS..114E5122F | doi-access = free }}</ref> but in other systems, different host factors may be required<ref>{{cite journal | vauthors = Rollie C, Graham S, Rouillon C, White MF | title = Prespacer processing and specific integration in a Type I-A CRISPR system | journal = Nucleic Acids Research | volume = 46 | issue = 3 | pages = 1007–1020 | date = February 2018 | pmid = 29228332 | pmc = 5815122 | doi = 10.1093/nar/gkx1232 }}</ref> |
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==== Protospacer adjacent motifs ==== |
==== Protospacer adjacent motifs (PAM)==== |
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{{Main|Protospacer adjacent motif}} |
{{Main|Protospacer adjacent motif}} |
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Bioinformatic analysis of regions of phage genomes that were excised as spacers (termed protospacers) revealed that they were not randomly selected but instead were found adjacent to short ( |
Bioinformatic analysis of regions of phage genomes that were excised as spacers (termed protospacers) revealed that they were not randomly selected but instead were found adjacent to short (3–5 bp) DNA sequences termed [[protospacer adjacent motif]]s (PAM). Analysis of CRISPR-Cas systems showed PAMs to be important for type I and type II, but not type III systems during acquisition.<ref name="pmid16079334"/><ref name="pmid18065539">{{cite journal | vauthors = Horvath P, Romero DA, Coûté-Monvoisin AC, Richards M, Deveau H, Moineau S, Boyaval P, Fremaux C, Barrangou R | author-link9=Rodolphe Barrangou | title = Diversity, activity, and evolution of CRISPR loci in ''Streptococcus thermophilus'' | journal = Journal of Bacteriology | volume = 190 | issue = 4 | pages = 1401–1412 | date = February 2008 | pmid = 18065539 | pmc = 2238196 | doi = 10.1128/JB.01415-07 }}</ref><ref name="pmid18065545">{{cite journal | vauthors = Deveau H, Barrangou R, Garneau JE, Labonté J, Fremaux C, Boyaval P, Romero DA, Horvath P, Moineau S | author-link2=Rodolphe Barrangou | title = Phage response to CRISPR-encoded resistance in ''Streptococcus thermophilus'' | journal = Journal of Bacteriology | volume = 190 | issue = 4 | pages = 1390–1400 | date = February 2008 | pmid = 18065545 | pmc = 2238228 | doi = 10.1128/JB.01412-07 }}</ref><ref name="pmid19246744">{{cite journal | vauthors = Mojica FJ, Díez-Villaseñor C, García-Martínez J, Almendros C | title = Short motif sequences determine the targets of the prokaryotic CRISPR defence system | journal = Microbiology | volume = 155 | issue = Pt 3 | pages = 733–740 | date = March 2009 | pmid = 19246744 | doi = 10.1099/mic.0.023960-0 | doi-access = free }}</ref><ref name="pmid19239620">{{cite journal | vauthors = Lillestøl RK, Shah SA, Brügger K, Redder P, Phan H, Christiansen J, Garrett RA | title = CRISPR families of the crenarchaeal genus Sulfolobus: bidirectional transcription and dynamic properties | journal = Molecular Microbiology | volume = 72 | issue = 1 | pages = 259–272 | date = April 2009 | pmid = 19239620 | doi = 10.1111/j.1365-2958.2009.06641.x }}</ref><ref name="pmid19143596">{{cite journal | vauthors = Shah SA, Hansen NR, Garrett RA | title = Distribution of CRISPR spacer matches in viruses and plasmids of crenarchaeal acidothermophiles and implications for their inhibitory mechanism | journal = Biochemical Society Transactions | volume = 37 | issue = Pt 1 | pages = 23–28 | date = February 2009 | pmid = 19143596 | doi = 10.1042/BST0370023 }}</ref> In type I and type II systems, protospacers are excised at positions adjacent to a PAM sequence, with the other end of the spacer cut using a ruler mechanism, thus maintaining the regularity of the spacer size in the CRISPR array.<ref name="pmid23445770">{{cite journal | vauthors = Díez-Villaseñor C, Guzmán NM, Almendros C, García-Martínez J, Mojica FJ | title = CRISPR-spacer integration reporter plasmids reveal distinct genuine acquisition specificities among CRISPR-Cas I-E variants of ''Escherichia coli'' | journal = RNA Biology | volume = 10 | issue = 5 | pages = 792–802 | date = May 2013 | pmid = 23445770 | pmc = 3737337 | doi = 10.4161/rna.24023 }}</ref><ref name="pmid22834906">{{cite journal | vauthors = Erdmann S, Garrett RA | title = Selective and hyperactive uptake of foreign DNA by adaptive immune systems of an archaeon via two distinct mechanisms | journal = Molecular Microbiology | volume = 85 | issue = 6 | pages = 1044–1056 | date = September 2012 | pmid = 22834906 | pmc = 3468723 | doi = 10.1111/j.1365-2958.2012.08171.x }}</ref> The conservation of the PAM sequence differs between CRISPR-Cas systems and appears to be evolutionarily linked to Cas1 and the [[Leader sequence (mRNA)|leader sequence]].<ref name="pmid19143596"/><ref name="pmid23403393">{{cite journal | vauthors = Shah SA, Erdmann S, Mojica FJ, Garrett RA | title = Protospacer recognition motifs: mixed identities and functional diversity | journal = RNA Biology | volume = 10 | issue = 5 | pages = 891–899 | date = May 2013 | pmid = 23403393 | pmc = 3737346 | doi = 10.4161/rna.23764 }}</ref> |
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New spacers are added to a CRISPR array in a directional manner,<ref name="pmid15758212" |
New spacers are added to a CRISPR array in a directional manner,<ref name="pmid15758212"/> occurring preferentially,<ref name="pmid17894817">{{cite journal | vauthors = Tyson GW, Banfield JF | title = Rapidly evolving CRISPRs implicated in acquired resistance of microorganisms to viruses | journal = Environmental Microbiology | volume = 10 | issue = 1 | pages = 200–207 | date = January 2008 | pmid = 17894817 | doi = 10.1111/j.1462-2920.2007.01444.x | bibcode = 2008EnvMi..10..200T }}</ref><ref name="pmid18065539"/><ref name="pmid18065545"/><ref name="pmid18497291">{{cite journal | vauthors = Andersson AF, Banfield JF | title = Virus population dynamics and acquired virus resistance in natural microbial communities | journal = Science | volume = 320 | issue = 5879 | pages = 1047–1050 | date = May 2008 | pmid = 18497291 | doi = 10.1126/science.1157358 | bibcode = 2008Sci...320.1047A }}</ref><ref name="pmid21149389">{{cite journal | vauthors = Pride DT, Sun CL, Salzman J, Rao N, Loomer P, Armitage GC, Banfield JF, Relman DA | title = Analysis of streptococcal CRISPRs from human saliva reveals substantial sequence diversity within and between subjects over time | journal = Genome Research | volume = 21 | issue = 1 | pages = 126–136 | date = January 2011 | pmid = 21149389 | pmc = 3012920 | doi = 10.1101/gr.111732.110 }}</ref> but not exclusively, adjacent<ref name="pmid19239620"/><ref name="pmid22834906"/> to the leader sequence. Analysis of the type I-E system from ''E. coli'' demonstrated that the first direct repeat adjacent to the leader sequence is copied, with the newly acquired spacer inserted between the first and second direct repeats.<ref name="pmid22402487"/><ref name="pmid23445770"/> |
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The PAM sequence appears to be important during spacer insertion in type I-E systems. That sequence contains a strongly conserved final nucleotide (nt) adjacent to the first nt of the protospacer. This nt becomes the final base in the first direct repeat.<ref name="pmid22558257" |
The PAM sequence appears to be important during spacer insertion in type I-E systems. That sequence contains a strongly conserved final nucleotide (nt) adjacent to the first nt of the protospacer. This nt becomes the final base in the first direct repeat.<ref name="pmid22558257"/><ref name="pmid22771574">{{cite journal | vauthors = Goren MG, Yosef I, Auster O, Qimron U | title = Experimental definition of a clustered regularly interspaced short palindromic duplicon in ''Escherichia coli'' | journal = Journal of Molecular Biology | volume = 423 | issue = 1 | pages = 14–16 | date = October 2012 | pmid = 22771574 | doi = 10.1016/j.jmb.2012.06.037 }}</ref><ref name="pmid22781758">{{cite journal | vauthors = Datsenko KA, Pougach K, Tikhonov A, Wanner BL, Severinov K, Semenova E | title = Molecular memory of prior infections activates the CRISPR/Cas adaptive bacterial immunity system | journal = Nature Communications | volume = 3 | page = 945 | date = July 2012 | pmid = 22781758 | doi = 10.1038/ncomms1937 | bibcode = 2012NatCo...3..945D | doi-access = free }}</ref> This suggests that the spacer acquisition machinery generates single-stranded overhangs in the second-to-last position of the direct repeat and in the PAM during spacer insertion. However, not all CRISPR-Cas systems appear to share this mechanism as PAMs in other organisms do not show the same level of conservation in the final position.<ref name="pmid23403393"/> It is likely that in those systems, a blunt end is generated at the very end of the direct repeat and the protospacer during acquisition. |
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==== Insertion variants ==== |
==== Insertion variants ==== |
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Analysis of ''[[Sulfolobus solfataricus]]'' CRISPRs revealed further complexities to the canonical model of spacer insertion, as one of its six CRISPR loci inserted new spacers randomly throughout its CRISPR array, as opposed to inserting closest to the leader sequence.<ref name="pmid22834906" |
Analysis of ''[[Sulfolobus solfataricus]]'' CRISPRs revealed further complexities to the canonical model of spacer insertion, as one of its six CRISPR loci inserted new spacers randomly throughout its CRISPR array, as opposed to inserting closest to the leader sequence.<ref name="pmid22834906"/> |
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Multiple CRISPRs contain many spacers to the same phage. The mechanism that causes this phenomenon was discovered in the type I-E system of ''E. coli''. A significant enhancement in spacer acquisition was detected where spacers already target the phage, even mismatches to the protospacer. This |
Multiple CRISPRs contain many spacers to the same phage. The mechanism that causes this phenomenon was discovered in the type I-E system of ''E. coli''. A significant enhancement in spacer acquisition was detected where spacers already target the phage, even mismatches to the protospacer. This 'priming' requires the Cas proteins involved in both acquisition and interference to interact with each other. Newly acquired spacers that result from the priming mechanism are always found on the same strand as the priming spacer.<ref name="pmid22558257"/><ref name="pmid22771574"/><ref name="pmid22781758"/> This observation led to the hypothesis that the acquisition machinery slides along the foreign DNA after priming to find a new protospacer.<ref name="pmid22781758"/> |
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=== Biogenesis === |
=== Biogenesis === |
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CRISPR-RNA (crRNA), which later guides the Cas nuclease to the target during the interference step, must be generated from the CRISPR sequence. |
CRISPR-RNA (crRNA), which later guides the Cas nuclease to the target during the interference step, must be generated from the CRISPR sequence. The crRNA is initially transcribed as part of a single long transcript encompassing much of the CRISPR array.<ref name="pmid20125085"/> This transcript is then cleaved by Cas proteins to form crRNAs. The mechanism to produce crRNAs differs among CRISPR-Cas systems. In type I-E and type I-F systems, the proteins Cas6e and Cas6f respectively, recognise stem-loops<ref name="pmid21572444">{{cite journal | vauthors = Gesner EM, Schellenberg MJ, Garside EL, George MM, Macmillan AM | title = Recognition and maturation of effector RNAs in a CRISPR interference pathway | journal = Nature Structural & Molecular Biology | volume = 18 | issue = 6 | pages = 688–692 | date = June 2011 | pmid = 21572444 | doi = 10.1038/nsmb.2042 }}</ref><ref name="pmid21572442">{{cite journal | vauthors = Sashital DG, Jinek M, Doudna JA | author-link3=Jennifer Doudna | title = An RNA-induced conformational change required for CRISPR RNA cleavage by the endoribonuclease Cse3 | journal = Nature Structural & Molecular Biology | volume = 18 | issue = 6 | pages = 680–687 | date = June 2011 | pmid = 21572442 | doi = 10.1038/nsmb.2043 }}</ref><ref name="pmid20829488">{{cite journal | vauthors = Haurwitz RE, Jinek M, Wiedenheft B, Zhou K, Doudna JA | author-link5=Jennifer Doudna | title = Sequence- and structure-specific RNA processing by a CRISPR endonuclease | journal = Science | volume = 329 | issue = 5997 | pages = 1355–1358 | date = September 2010 | pmid = 20829488 | pmc = 3133607 | doi = 10.1126/science.1192272 | bibcode = 2010Sci...329.1355H }}</ref> created by the pairing of identical repeats that flank the crRNA.<ref name="pmid17442114">{{cite journal | vauthors = Kunin V, Sorek R, Hugenholtz P | title = Evolutionary conservation of sequence and secondary structures in CRISPR repeats | journal = Genome Biology | volume = 8 | issue = 4 | pages = R61 | year = 2007 | pmid = 17442114 | pmc = 1896005 | doi = 10.1186/gb-2007-8-4-r61 | doi-access = free }}</ref> These Cas proteins cleave the longer transcript at the edge of the paired region, leaving a single crRNA along with a small remnant of the paired repeat region. |
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Type III systems also use Cas6, however their repeats do not produce stem-loops. Cleavage instead occurs by the longer transcript wrapping around the Cas6 to allow cleavage just upstream of the repeat sequence.<ref name="pmid19141480">{{cite journal | vauthors = Carte J, Wang R, Li H, Terns RM, Terns MP | title = Cas6 is an endoribonuclease that generates guide RNAs for invader defense in prokaryotes | journal = Genes & Development | volume = 22 | issue = 24 | pages = |
Type III systems also use Cas6, however, their repeats do not produce stem-loops. Cleavage instead occurs by the longer transcript wrapping around the Cas6 to allow cleavage just upstream of the repeat sequence.<ref name="pmid19141480">{{cite journal | vauthors = Carte J, Wang R, Li H, Terns RM, Terns MP | title = Cas6 is an endoribonuclease that generates guide RNAs for invader defense in prokaryotes | journal = Genes & Development | volume = 22 | issue = 24 | pages = 3489–3496 | date = December 2008 | pmid = 19141480 | pmc = 2607076 | doi = 10.1101/gad.1742908 }}</ref><ref name="pmid21300293">{{cite journal | vauthors = Wang R, Preamplume G, Terns MP, Terns RM, Li H | title = Interaction of the Cas6 riboendonuclease with CRISPR RNAs: recognition and cleavage | journal = Structure | volume = 19 | issue = 2 | pages = 257–264 | date = February 2011 | pmid = 21300293 | pmc = 3154685 | doi = 10.1016/j.str.2010.11.014 }}</ref><ref name="pmid24150936">{{cite journal | vauthors = Niewoehner O, Jinek M, Doudna JA | author-link3=Jennifer Doudna | title = Evolution of CRISPR RNA recognition and processing by Cas6 endonucleases | journal = Nucleic Acids Research | volume = 42 | issue = 2 | pages = 1341–1353 | date = January 2014 | pmid = 24150936 | pmc = 3902920 | doi = 10.1093/nar/gkt922 }}</ref> |
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Type II systems lack the Cas6 gene and instead utilize RNaseIII for cleavage. Functional type II systems encode an extra small RNA that is complementary to the repeat sequence, known as a [[trans-activating crRNA]] (tracrRNA).<ref name=" |
Type II systems lack the Cas6 gene and instead utilize RNaseIII for cleavage. Functional type II systems encode an extra small RNA that is complementary to the repeat sequence, known as a [[trans-activating crRNA]] (tracrRNA).<ref name="Deltcheva2011"/> Transcription of the tracrRNA and the primary CRISPR transcript results in base pairing and the formation of dsRNA at the repeat sequence, which is subsequently targeted by RNaseIII to produce crRNAs. Unlike the other two systems, the crRNA does not contain the full spacer, which is instead truncated at one end.<ref name="pmid22949671"/> |
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CrRNAs associate with Cas proteins to form ribonucleotide complexes that recognize foreign nucleic acids. CrRNAs show no preference between the coding and non-coding strands, which is indicative of an RNA-guided DNA-targeting system.<ref name="pmid19095942" |
CrRNAs associate with Cas proteins to form ribonucleotide complexes that recognize foreign nucleic acids. CrRNAs show no preference between the coding and non-coding strands, which is indicative of an RNA-guided DNA-targeting system.<ref name="pmid19095942"/><ref name="Garneau2010"/><ref name="pmid19120484"/><ref name="pmid22558257"/><ref name="pmid21646539">{{cite journal | vauthors = Semenova E, Jore MM, Datsenko KA, Semenova A, Westra ER, Wanner B, van der Oost J, Brouns SJ, Severinov K | title = Interference by clustered regularly interspaced short palindromic repeat (CRISPR) RNA is governed by a seed sequence | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 108 | issue = 25 | pages = 10098–10103 | date = June 2011 | pmid = 21646539 | pmc = 3121866 | doi = 10.1073/pnas.1104144108 | bibcode = 2011PNAS..10810098S | doi-access = free }}</ref><ref name="pmid21166892">{{cite journal | vauthors = Gudbergsdottir S, Deng L, Chen Z, Jensen JV, Jensen LR, She Q, Garrett RA | title = Dynamic properties of the Sulfolobus CRISPR/Cas and CRISPR/Cmr systems when challenged with vector-borne viral and plasmid genes and protospacers | journal = Molecular Microbiology | volume = 79 | issue = 1 | pages = 35–49 | date = January 2011 | pmid = 21166892 | pmc = 3025118 | doi = 10.1111/j.1365-2958.2010.07452.x }}</ref><ref name="pmid21385233">{{cite journal | vauthors = Manica A, Zebec Z, Teichmann D, Schleper C | title = In vivo activity of CRISPR-mediated virus defence in a hyperthermophilic archaeon | journal = Molecular Microbiology | volume = 80 | issue = 2 | pages = 481–491 | date = April 2011 | pmid = 21385233 | doi = 10.1111/j.1365-2958.2011.07586.x | doi-access = free }}</ref> The type I-E complex (commonly referred to as Cascade) requires five Cas proteins bound to a single crRNA.<ref name="pmid21460843">{{cite journal | vauthors = Jore MM, Lundgren M, van Duijn E, Bultema JB, Westra ER, Waghmare SP, Wiedenheft B, Pul U, Wurm R, Wagner R, Beijer MR, Barendregt A, Zhou K, Snijders AP, Dickman MJ, Doudna JA, Boekema EJ, Heck AJ, van der Oost J, Brouns SJ | author-link16 = Jennifer Doudna | title = Structural basis for CRISPR RNA-guided DNA recognition by Cascade | journal = Nature Structural & Molecular Biology | volume = 18 | issue = 5 | pages = 529–536 | date = May 2011 | pmid = 21460843 | doi = 10.1038/nsmb.2019 }}</ref><ref name="pmid21938068">{{cite journal | vauthors = Wiedenheft B, Lander GC, Zhou K, Jore MM, Brouns SJ, van der Oost J, Doudna JA, Nogales E | author-link7=Jennifer Doudna | title = Structures of the RNA-guided surveillance complex from a bacterial immune system | journal = Nature | volume = 477 | issue = 7365 | pages = 486–489 | date = September 2011 | pmid = 21938068 | doi = 10.1038/nature10402 | bibcode = 2011Natur.477..486W | pmc=4165517}}</ref> |
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=== Interference === |
=== Interference === |
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During the interference stage in type I systems the PAM sequence is recognized on the crRNA-complementary strand and is required along with crRNA annealing. In type I systems correct base pairing between the crRNA and the protospacer signals a conformational change in Cascade that recruits Cas3 for DNA degradation. |
During the interference stage in type I systems, the PAM sequence is recognized on the crRNA-complementary strand and is required along with crRNA annealing. In type I systems correct base pairing between the crRNA and the protospacer signals a conformational change in Cascade that recruits [[Cas3]] for DNA degradation. |
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Type II systems rely on a single multifunctional protein, [[Cas9]], for the interference step.<ref name="pmid22949671" |
Type II systems rely on a single multifunctional protein, [[Cas9]], for the interference step.<ref name="pmid22949671"/> Cas9 requires both the crRNA and the tracrRNA to function and cleave DNA using its dual HNH and RuvC/RNaseH-like endonuclease domains. Basepairing between the PAM and the phage genome is required in type II systems. However, the PAM is recognized on the same strand as the crRNA (the opposite strand to type I systems). |
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Type III systems, like type I require six or seven Cas proteins binding to crRNAs.<ref name="pmid22227115">{{cite journal | vauthors = Zhang J, Rouillon C, Kerou M, Reeks J, Brugger K, Graham S, Reimann J, Cannone G, Liu H, Albers SV, Naismith JH, Spagnolo L, White MF | title = Structure and mechanism of the CMR complex for CRISPR-mediated antiviral immunity | journal = Molecular Cell | volume = 45 | issue = 3 | pages = |
Type III systems, like type I require six or seven Cas proteins binding to crRNAs.<ref name="pmid22227115">{{cite journal | vauthors = Zhang J, Rouillon C, Kerou M, Reeks J, Brugger K, Graham S, Reimann J, Cannone G, Liu H, Albers SV, Naismith JH, Spagnolo L, White MF | title = Structure and mechanism of the CMR complex for CRISPR-mediated antiviral immunity | journal = Molecular Cell | volume = 45 | issue = 3 | pages = 303–313 | date = February 2012 | pmid = 22227115 | pmc = 3381847 | doi = 10.1016/j.molcel.2011.12.013 }}</ref><ref name="pmid19945378">{{cite journal | vauthors = Hale CR, Zhao P, Olson S, Duff MO, Graveley BR, Wells L, Terns RM, Terns MP | title = RNA-guided RNA cleavage by a CRISPR RNA-Cas protein complex | journal = Cell | volume = 139 | issue = 5 | pages = 945–956 | date = November 2009 | pmid = 19945378 | pmc = 2951265 | doi = 10.1016/j.cell.2009.07.040 }}</ref> The type III systems analysed from ''S. solfataricus'' and ''P. furiosus'' both target the mRNA of phages rather than phage DNA genome,<ref name="pmid23320564"/><ref name="pmid19945378"/> which may make these systems uniquely capable of targeting RNA-based phage genomes.<ref name="pmid22337052"/> Type III systems were also found to target DNA in addition to RNA using a different Cas protein in the complex, Cas10.<ref name="Estrella 2016">{{Cite journal |vauthors=Estrella MA, Kuo FT, Bailey S| doi = 10.1101/gad.273722.115| title =RNA-activated DNA cleavage by the Type III-B CRISPR–Cas effector complex| journal = [[Genes & Development]] | volume = 30 | issue = 4 | pages = 460–470 | year = 2016 | pmid = 26848046| pmc = 4762430 }}</ref> The DNA cleavage was shown to be transcription dependent.<ref name="Samai 2015">{{Cite journal |vauthors=Samai P, Pyenson N, Jiang W, Goldberg GW, Hatoum-Aslan A, Marraffini LA|author2-link=Nicholas Pyenson| doi = 10.1016/j.cell.2015.04.027| title =Co-transcriptional DNA and RNA Cleavage during Type III CRISPR-Cas Immunity| journal = Cell | volume = 161 | issue = 5 | pages = 1164–1174 | year = 2015 | pmid =25959775| pmc = 4594840 }}</ref> |
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The mechanism for distinguishing self from foreign DNA during interference is built into the crRNAs and is therefore likely common to all three systems. Throughout the distinctive maturation process of each major type, all crRNAs contain a spacer sequence and some portion of the repeat at one or both ends. It is the partial repeat sequence that prevents the CRISPR-Cas system from targeting the chromosome as base pairing beyond the spacer sequence signals self and prevents DNA cleavage.<ref name="pmid20072129">{{cite journal | vauthors = Marraffini LA, Sontheimer EJ | title = Self versus non-self discrimination during CRISPR RNA-directed immunity | journal = Nature | volume = 463 | issue = 7280 | pages = |
The mechanism for distinguishing self from foreign DNA during interference is built into the crRNAs and is therefore likely common to all three systems. Throughout the distinctive maturation process of each major type, all crRNAs contain a spacer sequence and some portion of the repeat at one or both ends. It is the partial repeat sequence that prevents the CRISPR-Cas system from targeting the chromosome as base pairing beyond the spacer sequence signals self and prevents DNA cleavage.<ref name="pmid20072129">{{cite journal | vauthors = Marraffini LA, Sontheimer EJ | title = Self versus non-self discrimination during CRISPR RNA-directed immunity | journal = Nature | volume = 463 | issue = 7280 | pages = 568–571 | date = January 2010 | pmid = 20072129 | pmc = 2813891 | doi = 10.1038/nature08703 | bibcode = 2010Natur.463..568M }}</ref> RNA-guided CRISPR enzymes are classified as [[Restriction enzyme#Type V|type V restriction enzymes]]. |
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== Evolution == |
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{{Infobox protein family |
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| Symbol = CRISPR_assoc |
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| Name = CRISPR associated protein |
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| image = PDB 1wj9 EBI.jpg |
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| width = |
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| caption = crystal structure of a crispr-associated protein from Thermus thermophilus |
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| Pfam = PF08798 |
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| Pfam_clan = CL0362 |
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| InterPro = IPR010179 |
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| SMART = |
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| PROSITE = |
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| MEROPS = |
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| SCOP = |
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| TCDB = |
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| OPM family = |
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| OPM protein = |
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| CAZy = |
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| CDD = cd09727 |
|||
}} |
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{{Infobox protein family |
{{Infobox protein family |
||
| Symbol = CRISPR_Cas2 |
| Symbol = CRISPR_Cas2 |
||
| Name = CRISPR associated protein Cas2 |
| Name = CRISPR associated protein Cas2 (adaptation RNase) |
||
| image = PDB 1zpw EBI.jpg |
| image = PDB 1zpw EBI.jpg |
||
| width = |
| width = |
||
| caption = |
| caption = Crystal structure of a hypothetical protein tt1823 from Thermus thermophilus |
||
| Pfam = PF09827 |
| Pfam = PF09827 |
||
| Pfam_clan = |
| Pfam_clan = |
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Line 218: | Line 265: | ||
{{Infobox protein family |
{{Infobox protein family |
||
| Symbol = CRISPR_Cse1 |
| Symbol = CRISPR_Cse1 |
||
| Name = CRISPR-associated protein Cse1 |
| Name = CRISPR-associated protein CasA/Cse1 (Type I effector DNase) |
||
| image = |
| image = |
||
| width = |
| width = |
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Line 236: | Line 283: | ||
}} |
}} |
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{{Infobox protein family |
{{Infobox protein family |
||
| Symbol = |
| Symbol = CRISPR_assoc |
||
| Name = CRISPR |
| Name = CRISPR associated protein CasC/Cse3/Cas6 (Type I effector RNase) |
||
| image = |
| image = PDB 1wj9 EBI.jpg |
||
| width = |
| width = |
||
| caption = |
| caption = Crystal structure of a crispr-associated protein from Thermus thermophilus |
||
| Pfam = |
| Pfam = PF08798 |
||
| Pfam_clan = |
| Pfam_clan = CL0362 |
||
| InterPro = |
| InterPro = IPR010179 |
||
| SMART = |
| SMART = |
||
| PROSITE = |
| PROSITE = |
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Line 252: | Line 299: | ||
| OPM protein = |
| OPM protein = |
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| CAZy = |
| CAZy = |
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| CDD = |
| CDD = cd09727 |
||
}} |
}} |
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The cas genes in the adaptor and effector modules of the CRISPR-Cas system are believed to have evolved from two different ancestral modules. A [[transposon]]-like element called [[casposon]] encoding the Cas1-like integrase and potentially other components of the adaptation module was inserted next to the ancestral effector module, which likely functioned as an independent innate immune system.<ref>{{cite journal | vauthors = Krupovic M, Béguin P, Koonin EV | author-link3=Eugene Koonin | title = Casposons: mobile genetic elements that gave rise to the CRISPR-Cas adaptation machinery | journal = Current Opinion in Microbiology | volume = 38 | pages = 36–43 | date = August 2017 | pmid = 28472712 | pmc = 5665730 | doi = 10.1016/j.mib.2017.04.004 }}</ref> The highly conserved cas1 and cas2 genes of the adaptor module evolved from the ancestral module while a variety of class 1 effector cas genes evolved from the ancestral effector module.<ref>{{cite journal | vauthors = Koonin EV, Makarova KS | author-link1=Eugene Koonin | title = CRISPR-Cas: evolution of an RNA-based adaptive immunity system in prokaryotes | journal = RNA Biology | volume = 10 | issue = 5 | pages = 679–686 | date = May 2013 | pmid = 23439366 | pmc = 3737325 | doi = 10.4161/rna.24022 }}</ref> The evolution of these various class 1 effector module cas genes was guided by various mechanisms, such as duplication events.<ref>{{cite journal | vauthors = Koonin EV, Makarova KS, Zhang F | author-link=Eugene Koonin | author-link3=Feng Zhang | title = Diversity, classification and evolution of CRISPR-Cas systems | journal = Current Opinion in Microbiology | volume = 37 | pages = 67–78 | date = June 2017 | pmid = 28605718 | pmc = 5776717 | doi = 10.1016/j.mib.2017.05.008 }}</ref> On the other hand, each type of class 2 effector module arose from subsequent independent insertions of mobile genetic elements.<ref name="Shmakov-2017">{{cite journal | vauthors = Shmakov S, Smargon A, Scott D, Cox D, Pyzocha N, Yan W, Abudayyeh OO, Gootenberg JS, Makarova KS, Wolf YI, Severinov K, Zhang F, Koonin EV | author-link13=Eugene Koonin | author-link12=Feng Zhang | title = Diversity and evolution of class 2 CRISPR-Cas systems | journal = Nature Reviews. Microbiology | volume = 15 | issue = 3 | pages = 169–182 | date = March 2017 | pmid = 28111461 | pmc = 5851899 | doi = 10.1038/nrmicro.2016.184 }}</ref> These mobile genetic elements took the place of the multiple gene effector modules to create single gene effector modules that produce large proteins which perform all the necessary tasks of the effector module.<ref name="Shmakov-2017"/> The spacer regions of CRISPR-Cas systems are taken directly from foreign mobile genetic elements and thus their long-term evolution is hard to trace.<ref>{{cite journal | vauthors = Kupczok A, Bollback JP | title = Probabilistic models for CRISPR spacer content evolution | journal = BMC Evolutionary Biology | volume = 13 | issue = 1 | page = 54 | date = February 2013 | pmid = 23442002 | pmc = 3704272 | doi = 10.1186/1471-2148-13-54 | bibcode = 2013BMCEE..13...54K | doi-access = free }}</ref> The non-random evolution of these spacer regions has been found to be highly dependent on the environment and the particular foreign mobile genetic elements it contains.<ref>{{cite journal | vauthors = Sternberg SH, Richter H, Charpentier E, Qimron U | title = Adaptation in CRISPR-Cas Systems | journal = Molecular Cell | volume = 61 | issue = 6 | pages = 797–808 | date = March 2016 | pmid = 26949040 | doi = 10.1016/j.molcel.2016.01.030 | hdl = 21.11116/0000-0003-E74E-2 | hdl-access = free }}</ref> |
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== Evolution == |
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A [[bioinformatic]] study has suggested that CRISPRs are evolutionarily conserved and cluster into related types. Many show signs of a conserved secondary structure.<ref name="pmid17442114" /> |
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CRISPR |
CRISPR-Cas can immunize bacteria against certain phages and thus halt transmission. For this reason, [[Eugene Koonin|Koonin]] described CRISPR-Cas as a [[Lamarckism|Lamarckian]] inheritance mechanism.<ref name="pmid19906303">{{cite journal | vauthors = Koonin EV, Wolf YI | author-link=Eugene Koonin | title = Is evolution Darwinian or/and Lamarckian? | journal = Biology Direct | volume = 4 | page = 42 | date = November 2009 | pmid = 19906303 | pmc = 2781790 | doi = 10.1186/1745-6150-4-42 | doi-access=free }}</ref> However, this was disputed by a critic who noted, "We should remember [Lamarck] for the good he contributed to science, not for things that resemble his theory only superficially. Indeed, thinking of CRISPR and other phenomena as Lamarckian only obscures the simple and elegant way evolution really works".<ref>{{cite journal | vauthors = Weiss A | title = Lamarckian Illusions | journal = Trends in Ecology & Evolution | volume = 30 | issue = 10 | pages = 566–568 | date = October 2015 | pmid = 26411613 | doi = 10.1016/j.tree.2015.08.003 | doi-access = free | bibcode = 2015TEcoE..30..566W }}</ref> But as more recent studies have been conducted, it has become apparent that the acquired spacer regions of CRISPR-Cas systems are indeed a form of Lamarckian evolution because they are genetic mutations that are acquired and then passed on.<ref name="Koonin-2016">{{cite journal | vauthors = Koonin EV, Wolf YI | author-link=Eugene Koonin | title = Just how Lamarckian is CRISPR-Cas immunity: the continuum of evolvability mechanisms | journal = Biology Direct | volume = 11 | issue = 1 | page = 9 | date = February 2016 | pmid = 26912144 | pmc = 4765028 | doi = 10.1186/s13062-016-0111-z | doi-access=free }}</ref> On the other hand, the evolution of the Cas gene machinery that facilitates the system evolves through classic Darwinian evolution.<ref name="Koonin-2016"/> |
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=== Coevolution === |
=== Coevolution === |
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Analysis of CRISPR sequences revealed [[coevolution]] of host and viral genomes.<ref>{{cite journal| |
Analysis of CRISPR sequences revealed [[coevolution]] of host and viral genomes.<ref>{{cite journal | vauthors = Heidelberg JF, Nelson WC, Schoenfeld T, Bhaya D | title = Germ warfare in a microbial mat community: CRISPRs provide insights into the co-evolution of host and viral genomes | journal = PLOS ONE | volume = 4 | issue = 1 | pages = e4169 | year = 2009 | pmid = 19132092 | pmc = 2612747 | doi = 10.1371/journal.pone.0004169 | bibcode = 2009PLoSO...4.4169H | veditors = Ahmed N | doi-access = free }}</ref> |
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The basic model of CRISPR evolution is newly incorporated spacers driving phages to mutate their genomes to avoid the bacterial immune response, creating diversity in both the phage and host populations. To |
The basic model of CRISPR evolution is newly incorporated spacers driving phages to mutate their genomes to avoid the bacterial immune response, creating diversity in both the phage and host populations. To resist a phage infection, the sequence of the CRISPR spacer must correspond perfectly to the sequence of the target phage gene. Phages can continue to infect their hosts' given point mutations in the spacer.<ref name="pmid20072129"/> Similar stringency is required in PAM or the bacterial strain remains phage sensitive.<ref name="pmid18065545"/><ref name="pmid20072129"/> |
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=== Rates === |
=== Rates === |
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A study of 124 ''S. thermophilus'' strains showed that 26% of all spacers were unique and that different CRISPR loci showed different rates of spacer acquisition.<ref name="pmid18065539" |
A study of 124 ''S. thermophilus'' strains showed that 26% of all spacers were unique and that different CRISPR loci showed different rates of spacer acquisition.<ref name="pmid18065539"/> Some CRISPR loci evolve more rapidly than others, which allowed the strains' phylogenetic relationships to be determined. A [[Comparative genomics|comparative genomic]] analysis showed that ''E. coli'' and ''[[Salmonella enterica|S. enterica]]'' evolve much more slowly than ''S. thermophilus''. The latter's strains that diverged 250,000 years ago still contained the same spacer complement.<ref name="pmid20559554">{{cite journal | vauthors = Touchon M, Rocha EP | title = The small, slow and specialized CRISPR and anti-CRISPR of Escherichia and Salmonella | journal = PLOS ONE | volume = 5 | issue = 6 | pages = e11126 | date = June 2010 | pmid = 20559554 | pmc = 2886076 | doi = 10.1371/journal.pone.0011126 | veditors = Randau L | bibcode = 2010PLoSO...511126T | doi-access = free }}</ref> |
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[[metagenomics|Metagenomic]] analysis of two acid |
[[metagenomics|Metagenomic]] analysis of two acid-mine-drainage [[biofilm]]s showed that one of the analyzed CRISPRs contained extensive deletions and spacer additions versus the other biofilm, suggesting a higher phage activity/prevalence in one community than the other.<ref name="pmid17894817"/> In the oral cavity, a temporal study determined that 7–22% of spacers were shared over 17 months within an individual while less than 2% were shared across individuals.<ref name="pmid21149389"/> |
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From the same environment a single strain was tracked using [[PCR]] primers specific to its CRISPR system. Broad-level results of spacer presence/absence showed significant diversity. However, this CRISPR added |
From the same environment, a single strain was tracked using [[Polymerase chain reaction|PCR]] primers specific to its CRISPR system. Broad-level results of spacer presence/absence showed significant diversity. However, this CRISPR added three spacers over 17 months,<ref name="pmid21149389"/> suggesting that even in an environment with significant CRISPR diversity some loci evolve slowly. |
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CRISPRs were analysed from the metagenomes produced for the [[ |
CRISPRs were analysed from the metagenomes produced for the [[Human Microbiome Project]].<ref name="pmid22719260">{{cite journal | vauthors = Rho M, Wu YW, Tang H, Doak TG, Ye Y | title = Diverse CRISPRs evolving in human microbiomes | journal = PLOS Genetics | volume = 8 | issue = 6 | pages = e1002441 | year = 2012 | pmid = 22719260 | pmc = 3374615 | doi = 10.1371/journal.pgen.1002441 | doi-access = free }}</ref> Although most were body-site specific, some within a body site are widely shared among individuals. One of these loci originated from [[streptococcal]] species and contained ≈15,000 spacers, 50% of which were unique. Similar to the targeted studies of the oral cavity, some showed little evolution over time.<ref name="pmid22719260"/> |
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CRISPR evolution was studied in [[chemostat]]s using ''S. thermophilus'' to directly examine spacer acquisition rates. In one week, ''S. thermophilus'' strains acquired up to three spacers when challenged with a single phage.<ref name="pmid23057534">{{cite journal | vauthors = Sun CL, Barrangou R, Thomas BC, Horvath P, Fremaux C, Banfield JF | title = Phage mutations in response to CRISPR diversification in a bacterial population | journal = Environmental Microbiology | volume = 15 | issue = 2 | pages = |
CRISPR evolution was studied in [[chemostat]]s using ''S. thermophilus'' to directly examine spacer acquisition rates. In one week, ''S. thermophilus'' strains acquired up to three spacers when challenged with a single phage.<ref name="pmid23057534">{{cite journal | vauthors = Sun CL, Barrangou R, Thomas BC, Horvath P, Fremaux C, Banfield JF | author-link2=Rodolphe Barrangou | title = Phage mutations in response to CRISPR diversification in a bacterial population | journal = Environmental Microbiology | volume = 15 | issue = 2 | pages = 463–470 | date = February 2013 | pmid = 23057534 | doi = 10.1111/j.1462-2920.2012.02879.x | bibcode=2013EnvMi..15..463S }}</ref> During the same interval, the phage developed [[single-nucleotide polymorphism]]s that became fixed in the population, suggesting that targeting had prevented phage replication absent these mutations.<ref name="pmid23057534"/> |
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Another ''S. thermophilus'' experiment showed that phages can infect and replicate in hosts that have only one targeting spacer. Yet another showed that sensitive hosts can exist in environments with high |
Another ''S. thermophilus'' experiment showed that phages can infect and replicate in hosts that have only one targeting spacer. Yet another showed that sensitive hosts can exist in environments with high-phage titres.<ref name="pmid24586036">{{cite journal | vauthors = Kuno S, Sako Y, Yoshida T | title = Diversification of CRISPR within coexisting genotypes in a natural population of the bloom-forming cyanobacterium Microcystis aeruginosa | journal = Microbiology | volume = 160 | issue = Pt 5 | pages = 903–916 | date = May 2014 | pmid = 24586036 | doi = 10.1099/mic.0.073494-0 | doi-access = free }}</ref> The chemostat and observational studies suggest many nuances to CRISPR and phage (co)evolution. |
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== Identification == |
== Identification == |
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CRISPRs are widely distributed among bacteria and archaea<ref name="pmid24728998"/> and show some sequence similarities.<ref name="pmid17442114"/> Their most notable characteristic is their repeating spacers and direct repeats. This characteristic makes CRISPRs easily identifiable in long sequences of DNA, since the number of repeats decreases the likelihood of a false positive match.<ref>{{cite journal | vauthors = Sorek R, Kunin V, Hugenholtz P | title = CRISPR—a widespread system that provides acquired resistance against phages in bacteria and archaea | journal = Nature Reviews. Microbiology | volume = 6 | issue = 3 | pages = 181–186 | date = March 2008 | pmid = 18157154 | doi = 10.1038/nrmicro1793 | quote = Table 1: Web resources for CRISPR analysis }}</ref> |
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Analysis of CRISPRs in metagenomic data is more challenging, as CRISPR loci do not typically assemble, due to their repetitive nature or through strain variation, which confuses assembly algorithms. Where many reference genomes are available, [[polymerase chain reaction]] (PCR) can be used to amplify CRISPR arrays and analyse spacer content.<ref name="pmid18065539"/><ref name="pmid21149389"/><ref name="pmid22583485">{{cite journal | vauthors = Pride DT, Salzman J, Relman DA | title = Comparisons of clustered regularly interspaced short palindromic repeats and viromes in human saliva reveal bacterial adaptations to salivary viruses | journal = Environmental Microbiology | volume = 14 | issue = 9 | pages = 2564–2576 | date = September 2012 | pmid = 22583485 | pmc = 3424356 | doi = 10.1111/j.1462-2920.2012.02775.x | bibcode = 2012EnvMi..14.2564P }}</ref><ref name="pmid23701169">{{cite journal | vauthors = Held NL, Herrera A, Whitaker RJ | title = Reassortment of CRISPR repeat-spacer loci in Sulfolobus islandicus | journal = Environmental Microbiology | volume = 15 | issue = 11 | pages = 3065–3076 | date = November 2013 | pmid = 23701169 | doi = 10.1111/1462-2920.12146 | bibcode = 2013EnvMi..15.3065H }}</ref><ref name="pmid20927396">{{cite journal | vauthors = Held NL, Herrera A, Cadillo-Quiroz H, Whitaker RJ | title = CRISPR associated diversity within a population of Sulfolobus islandicus | journal = PLOS ONE | volume = 5 | issue = 9 | pages = e12988 | date = September 2010 | pmid = 20927396 | pmc = 2946923 | doi = 10.1371/journal.pone.0012988 | bibcode = 2010PLoSO...512988H | doi-access = free }}</ref><ref name="pmid31729390">{{cite journal | vauthors = Medvedeva S, Liu Y, Koonin EV, Severinov K, Prangishvili D, Krupovic M | title = Virus-borne mini-CRISPR arrays are involved in interviral conflicts | journal = Nature Communications | volume = 10 | issue = 1 | page = 5204 | date = November 2019 | pmid = 31729390 | pmc = 6858448 | doi = 10.1038/s41467-019-13205-2 | bibcode = 2019NatCo..10.5204M }}</ref> However, this approach yields information only for specifically targeted CRISPRs and for organisms with sufficient representation in public databases to design reliable polymerase PCR primers. Degenerate repeat-specific primers can be used to amplify CRISPR spacers directly from environmental samples; amplicons containing two or three spacers can be then computationally assembled to reconstruct long CRISPR arrays.<ref name="pmid31729390"/> |
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CRISPRs are widely distributed among bacteria and archaea<ref name="pmid24728998" /> and show some sequence similarities.<ref name="pmid17442114" /> Their most notable characteristic is their repeating spacers and direct repeats. This characteristic makes CRISPRs easily identifiable in long sequences of DNA, since the number of repeats decreases the likelihood of a false positive match. Three programs used for CRISPR repeat identification search for regularly interspaced repeats in long sequences: CRT,<ref name="pmid17577412">{{cite journal | vauthors = Bland C, Ramsey TL, Sabree F, Lowe M, Brown K, Kyrpides NC, Hugenholtz P | title = CRISPR recognition tool (CRT): a tool for automatic detection of clustered regularly interspaced palindromic repeats | journal = BMC Bioinformatics | volume = 8 | pages = 209 | date = June 2007 | pmid = 17577412 | pmc = 1924867 | doi = 10.1186/1471-2105-8-209 }}</ref> PILER-CR<ref name="pmid17239253">{{cite journal | vauthors = Edgar RC | title = PILER-CR: fast and accurate identification of CRISPR repeats | journal = BMC Bioinformatics | volume = 8 | pages = 18 | date = January 2007 | pmid = 17239253 | pmc = 1790904 | doi = 10.1186/1471-2105-8-18 }}</ref> and CRISPRfinder.<ref name="pmid17537822">{{cite journal | vauthors = Grissa I, Vergnaud G, Pourcel C | title = CRISPRFinder: a web tool to identify clustered regularly interspaced short palindromic repeats | journal = Nucleic Acids Research | volume = 35 | issue = Web Server issue | pages = W52–7 | date = July 2007 | pmid = 17537822 | pmc = 1933234 | doi = 10.1093/nar/gkm360 }}</ref> |
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The alternative is to extract and reconstruct CRISPR arrays from shotgun metagenomic data. This is computationally more difficult, particularly with second generation sequencing technologies (e.g. 454, Illumina), as the short read lengths prevent more than two or three repeat units appearing in a single read. CRISPR identification in raw reads has been achieved using purely ''de novo'' identification<ref name="pmid23511966">{{cite journal | vauthors = Skennerton CT, Imelfort M, Tyson GW | title = Crass: identification and reconstruction of CRISPR from unassembled metagenomic data | journal = Nucleic Acids Research | volume = 41 | issue = 10 | pages = e105 | date = May 2013 | pmid = 23511966 | pmc = 3664793 | doi = 10.1093/nar/gkt183 }}</ref> or by using direct repeat sequences in partially assembled CRISPR arrays from [[contig]]s (overlapping DNA segments that together represent a consensus region of DNA)<ref name="pmid22719260"/> and direct repeat sequences from published genomes<ref name="pmid22732228">{{cite journal | vauthors = Stern A, Mick E, Tirosh I, Sagy O, Sorek R | title = CRISPR targeting reveals a reservoir of common phages associated with the human gut microbiome | journal = Genome Research | volume = 22 | issue = 10 | pages = 1985–1994 | date = October 2012 | pmid = 22732228 | pmc = 3460193 | doi = 10.1101/gr.138297.112 }}</ref> as a hook for identifying direct repeats in individual reads. |
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The alternative is to extract and reconstruct CRISPR arrays from shotgun metagenomic data. This is computationally more difficult, particularly with second generation sequencing technologies (e.g. 454, Illumina), as the short read lengths prevent more than two or three repeat units appearing in a single read. CRISPR identification in raw reads has been achieved using purely ''de novo'' identification<ref name="pmid23511966">{{cite journal | vauthors = Skennerton CT, Imelfort M, Tyson GW | title = Crass: identification and reconstruction of CRISPR from unassembled metagenomic data | journal = Nucleic Acids Research | volume = 41 | issue = 10 | pages = e105 | date = May 2013 | pmid = 23511966 | pmc = 3664793 | doi = 10.1093/nar/gkt183 }}</ref> or by using direct repeat sequences in partially assembled CRISPR arrays from [[contig]]s (overlapping DNA segments that together represent a consensus region of DNA)<ref name="pmid22719260" /> and direct repeat sequences from published genomes<ref name="pmid22732228">{{cite journal | vauthors = Stern A, Mick E, Tirosh I, Sagy O, Sorek R | title = CRISPR targeting reveals a reservoir of common phages associated with the human gut microbiome | journal = Genome Research | volume = 22 | issue = 10 | pages = 1985–94 | date = October 2012 | pmid = 22732228 | pmc = 3460193 | doi = 10.1101/gr.138297.112 }}</ref> as a hook for identifying direct repeats in individual reads. |
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== Use by phages == |
== Use by phages == |
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Another way for bacteria to defend against phage infection is by having [[genomic island|chromosomal islands]]. A subtype of chromosomal islands called phage-inducible chromosomal island (PICI) is excised from a bacterial chromosome upon phage infection and can inhibit phage replication.<ref name="pmid20634809">{{cite journal | vauthors = Novick RP, Christie GE, Penadés JR | title = The phage-related chromosomal islands of Gram-positive bacteria | journal = Nature Reviews Microbiology | volume = 8 | issue = 8 | pages = 541–551 | date = August 2010 | pmid = 20634809 | pmc = 3522866 | doi = 10.1038/nrmicro2393 }}</ref> PICIs are induced, excised, replicated, and finally packaged into small capsids by certain staphylococcal temperate phages. PICIs use several mechanisms to block phage reproduction. In the first mechanism, PICI-encoded Ppi differentially blocks phage maturation by binding or interacting specifically with phage TerS, hence blocking phage TerS/TerL complex formation responsible for phage DNA packaging. In the second mechanism PICI CpmAB redirects the phage capsid morphogenetic protein to make 95% of SaPI-sized capsid and phage DNA can package only 1/3rd of their genome in these small capsids and hence become nonviable phage.<ref>{{cite journal|vauthors=Ram G, Chen J, Kumar K, Ross HF, Ubeda C, Damle PK, Lane KD, Penadés JR, Christie GE, Novick RP|date=October 2012|title=Staphylococcal pathogenicity island interference with helper phage reproduction is a paradigm of molecular parasitism|journal=Proceedings of the National Academy of Sciences of the United States of America|volume=109|issue=40|pages=16300–16305|doi=10.1073/pnas.1204615109|pmc=3479557|pmid=22991467|bibcode=2012PNAS..10916300R|doi-access=free}}</ref> The third mechanism involves two proteins, PtiA and PtiB, that target the LtrC, which is responsible for the production of virion and lysis proteins. This interference mechanism is modulated by a modulatory protein, PtiM, binds to one of the interference-mediating proteins, PtiA, and hence achieves the required level of interference.<ref>{{cite journal|vauthors=Ram G, Chen J, Ross HF, Novick RP|date=October 2014|title=Precisely modulated pathogenicity island interference with late phage gene transcription|journal=Proceedings of the National Academy of Sciences of the United States of America|volume=111|issue=40|pages=14536–14541|doi=10.1073/pnas.1406749111|pmc=4209980|pmid=25246539|bibcode=2014PNAS..11114536R|doi-access=free}}</ref> |
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One study showed that lytic ICP1 phage, which specifically targets ''[[Vibrio cholerae]]'' [[serogroup]] O1, has acquired a CRISPR-Cas system that targets a ''V. cholera'' PICI-like element. The system has 2 CRISPR loci and 9 Cas genes. It seems to be [[Homology (biology)|homologous]] to the I-F system found in ''[[Yersinia pestis]]''. Moreover, like the bacterial CRISPR-Cas system, ICP1 CRISPR-Cas can acquire new sequences, which allows phage and host to co-evolve.<ref name="pmid23446421">{{cite journal | vauthors = Seed KD, Lazinski DW, Calderwood SB, Camilli A | title = A bacteriophage encodes its own CRISPR/Cas adaptive response to evade host innate immunity | journal = Nature | volume = 494 | issue = 7438 | pages = 489–491 | date = February 2013 | pmid = 23446421 | pmc = 3587790 | doi = 10.1038/nature11927 | bibcode = 2013Natur.494..489S }}</ref><ref name="Boyd">{{cite journal | vauthors = Boyd CM, Angermeyer A, Hays SG, Barth ZK, Patel KM, Seed KD | title = Bacteriophage ICP1: A Persistent Predator of ''Vibrio cholerae'' | journal = Annual Review of Virology | volume = 8 | issue = 1 | pages = 285–304 | date = September 2021 | pmid = 34314595 | doi = 10.1146/annurev-virology-091919-072020 | pmc = 9040626 |issn=2327-056X | doi-access = free }}</ref> |
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Certain archaeal viruses were shown to carry mini-CRISPR arrays containing one or two spacers. It has been shown that spacers within the virus-borne CRISPR arrays target other viruses and plasmids, suggesting that mini-CRISPR arrays represent a mechanism of heterotypic superinfection exclusion and participate in interviral conflicts.<ref name="pmid31729390"/> |
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Another way for bacteria to defend against phage infection is by having [[genomic island|chromosomal islands]]. A subtype of chromosomal islands called phage-inducible chromosomal island (PICI) is excised from a bacterial chromosome upon phage infection and can inhibit phage replication.<ref name="pmid20634809">{{cite journal | vauthors = Novick RP, Christie GE, Penadés JR | title = The phage-related chromosomal islands of Gram-positive bacteria | journal = Nature Reviews Microbiology | volume = 8 | issue = 8 | pages = 541–51 | date = August 2010 | pmid = 20634809 | pmc = 3522866 | doi = 10.1038/nrmicro2393 }}</ref> The mechanisms that induce PICI excision and how PICI inhibits phage replication are not well understood. One study showed that lytic ICP1 phage, which specifically targets ''[[Vibrio cholerae]]'' [[serogroup]] O1, has acquired a CRISPR/Cas system that targets a ''V. cholera'' PICI-like element. The system has 2 CRISPR loci and 9 Cas genes. It seems to be [[Homology (biology)|homologous]] to the 1-F system found in ''[[Yersinia pestis]]''. Moreover, like the bacterial CRISPR/Cas system, ICP1 CRISPR/Cas can acquire new sequences, which allows phage and host to co-evolve.<ref name="pmid23446421">{{cite journal | vauthors = Seed KD, Lazinski DW, Calderwood SB, Camilli A | title = A bacteriophage encodes its own CRISPR/Cas adaptive response to evade host innate immunity | journal = Nature | volume = 494 | issue = 7438 | pages = 489–91 | date = February 2013 | pmid = 23446421 | pmc = 3587790 | doi = 10.1038/nature11927 | bibcode = 2013Natur.494..489S }}</ref> |
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== Applications == |
== Applications == |
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{{main|CRISPR gene editing}} |
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CRISPR gene editing is a revolutionary technology that allows for precise, targeted modifications to the DNA of living organisms. Developed from a natural defense mechanism found in bacteria, CRISPR-Cas9 is the most commonly used system, that allows "cutting" of DNA at specific locations and either delete, modify, or insert genetic material. This technology has transformed fields such as genetics, medicine,<ref name="pmid39081515">{{cite journal | vauthors = Feng Q, Li Q, Zhou H, Wang Z, Lin C, Jiang Z, Liu T, Wang D | title = CRISPR technology in human diseases | journal = Medcomm | volume = 5 | issue = 8 | pages = e672 | date = August 2024 | pmid = 39081515 | pmc = 11286548 | doi = 10.1002/mco2.672 }}</ref><ref name="pmid39118151">{{cite journal | vauthors = Li T, Li S, Kang Y, Zhou J, Yi M | title = Harnessing the evolving CRISPR/Cas9 for precision oncology | journal = Journal of Translational Medicine | volume = 22 | issue = 1 | pages = 749 | date = August 2024 | pmid = 39118151 | doi = 10.1186/s12967-024-05570-4 | doi-access = free | pmc = 11312220 }}</ref> and agriculture,<ref name="pmid39065411">{{cite journal | vauthors = Mishra S, Nayak S, Tuteja N, Poosapati S, Swain DM, Sahoo RK | title = CRISPR/Cas-Mediated Genome Engineering in Plants: Application and Prospectives | journal = Plants | location = Basel, Switzerland | volume = 13 | issue = 14 | date = July 2024 | page = 1884 | pmid = 39065411 | pmc = 11279650 | doi = 10.3390/plants13141884 | doi-access = free }}</ref><ref name="pmid39115550">{{cite journal | vauthors = Kaur R, Gupta S, Chauhan A, Mishra V, Sharma MK, Singh J | title = Harnessing the power of clustered regularly interspaced short palindromic repeats (CRISPR) based microfluidics for next-generation molecular diagnostics | journal = Molecular Biology Reports | volume = 51 | issue = 1 | pages = 896 | date = August 2024 | pmid = 39115550 | doi = 10.1007/s11033-024-09840-8 }}</ref> offering potential treatments for genetic disorders, advancements in crop engineering, and research into the fundamental workings of life. However, its ethical implications and potential unintended consequences have sparked significant debate.<ref name="pmid28879860">{{cite journal | vauthors = Shinwari ZK, Tanveer F, Khalil AT | title = Ethical Issues Regarding CRISPR Mediated Genome Editing | journal = Current Issues in Molecular Biology | volume = 26 | issue = | pages = 103–110 | date = 2018 | pmid = 28879860 | doi = 10.21775/cimb.026.103 | doi-access = free }}</ref><ref name="pmid38059350">{{cite journal | vauthors = Kozan DW, Farber SA | title = Is It Ever Wise to Edit Wild-Type Alleles? Engineered CRISPR Alleles Versus Millions of Years of Human Evolution | journal = Arteriosclerosis, Thrombosis, and Vascular Biology | volume = 44 | issue = 2 | pages = 328–333 | date = February 2024 | pmid = 38059350 | doi = 10.1161/ATVBAHA.123.318069 | pmc = 10948015 | pmc-embargo-date = February 1, 2025 }}</ref> |
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By the end of 2014 some 1000 research papers had been published that mentioned CRISPR.<ref>{{cite journal | vauthors = Doudna JA, Charpentier E | title = Genome editing. The new frontier of genome engineering with CRISPR-Cas9 | journal = Science | volume = 346 | issue = 6213 | pages = 1258096 | date = November 2014 | pmid = 25430774 | doi = 10.1126/science.1258096 }}</ref><ref name="NatNews2015">{{cite journal | vauthors = Ledford H | title = CRISPR, the disruptor | journal = Nature | volume = 522 | issue = 7554 | pages = 20–4 | date = June 2015 | pmid = 26040877 | doi = 10.1038/522020a | bibcode = 2015Natur.522...20L }}</ref> The technology had been used to functionally inactivate genes in human cell lines and cells, to study ''[[Candida albicans]]'', to modify [[yeasts]] used to make [[biofuels]] and to [[genetically modified crops|genetically modify crop]] strains.<ref name="NatNews2015" /> CRISPR can also be used to change mosquitos so they cannot transmit diseases such as malaria.<ref name="pmid26849518">{{cite journal | vauthors = Alphey L | title = Can CRISPR-Cas9 gene drives curb malaria? | journal = Nature Biotechnology | volume = 34 | issue = 2 | pages = 149–50 | year = 2016 | pmid = 26849518 | doi = 10.1038/nbt.3473 }}</ref> |
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== See also == |
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CRISPR-based re-evaluations of claims for gene-disease relationships have led to the discovery of potentially important anomalies.<ref>{{cite journal | doi = 10.1038/nature.2017.21763 |title=CRISPR studies muddy results of older gene research |journal=Nature |year=2017 |last1=Ledford |first1=Heidi | name-list-format = vanc }}</ref> |
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{{div col|colwidth=18em}} |
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[[File:DNA Repair.png|thumb|415x415px|DNA repair after double-strand break]] |
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* [[CRISPR activation]] |
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=== Predecessors === |
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* [[Anti-CRISPR]] |
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In the early 2000s, researchers developed [[zinc finger nuclease]]s, synthetic proteins whose [[DNA-binding domains]] enable them to create double-stranded breaks in DNA at specific points. In 2010, synthetic nucleases called [[transcription activator-like effector nuclease]]s (TALENs) provided an easier way to target a double-stranded break to a specific location on the DNA strand. Both zinc finger nucleases and TALENs require the creation of a custom protein for each targeted DNA sequence, which is a more difficult and time-consuming process than that for guide RNAs. CRISPRs are much easier to design because the process requires making only a short RNA sequence.<ref name="MIT">{{cite journal|last=Young|first=Susan|date=11 February 2014|title=CRISPR and Other Genome Editing Tools Boost Medical Research and Gene Therapy's Reach|url=http://www.technologyreview.com/review/524451/genome-surgery|location=Cambridge, Massachusetts|publisher=Massachusetts Institute of Technology|accessdate=2014-04-13|name-list-format=vanc|work=[[MIT Technology Review]]}}</ref> |
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=== Genome engineering === |
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CRISPR/Cas9 genome editing is carried out with a [[CRISPR#Cas genes and CRISPR subtypes|Type II]] CRISPR system. When utilized for genome editing, this system includes [[Cas9]], crRNA, tracrRNA along with an optional section of DNA repair template that is utilized in either non-homologous end joining (NHEJ) or homology directed repair (HDR). |
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[[File:CRISPR overview - en.svg|thumb|385x385px|Overview of CRISPR Cas9 plasmid construction<ref>{{cite web | title = CRISPR/Cas9 Plasmids | url = https://www.systembio.com/crispr-cas9/overview | website = www.systembio.com | accessdate = 2015-12-17 }}</ref><ref>{{cite web | title = CRISPR Cas9 Genome Editing | publisher = OriGene | url = http://www.origene.com/crispr-cas9/ | website = www.origene.com | accessdate = 2015-12-17 }}</ref>]] |
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==== Major components ==== |
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{| class="wikitable" |
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|- |
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! Component |
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! Function |
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|- |
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| [[List of RNAs|crRNA]] |
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| Contains the guide RNA that locates the correct section of host DNA along with a region that binds to [[Trans-activating crRNA|tracrRNA]] (generally in a [[Stem-loop|hairpin loop]] form) forming an active complex. |
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|- |
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| [[Trans-activating crRNA|tracrRNA]] |
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| Binds to [[List of RNAs|crRNA]] and forms an active complex. |
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|- |
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| sgRNA |
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| Single guide RNAs are a combined RNA consisting of a [[Trans-activating crRNA|tracrRNA]] and at least one [[List of RNAs|crRNA]] |
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|- |
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| Cas9 |
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| Protein whose active form is able to modify DNA. Many variants exist with differing functions (i.e. single strand nicking, double strand break, DNA binding) due to Cas9's DNA site recognition function. |
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|- |
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| Repair template |
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| DNA that guides the cellular repair process allowing insertion of a specific DNA sequence |
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|} |
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CRISPR/Cas9 often employs a [[plasmid]] to [[Transfection|transfect]] the target cells.<ref name="Ran_2013" /> The main components of this plasmid are displayed in the image and listed in the table. The crRNA needs to be designed for each application as this is the sequence that Cas9 uses to identify and directly bind to the cell's DNA. The crRNA must bind only where editing is desired. The repair template is designed for each application, as it must overlap with the sequences on either side of the cut and code for the insertion sequence. |
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Multiple crRNAs and the tracrRNA can be packaged together to form a single-guide RNA (sgRNA).<ref>{{cite thesis |url=https://archive.org/details/LyJosephP201311PhDThesis |title=Discovering Genes Responsible for Kidney Diseases |last=Ly |first=Joseph |year=2013 |type=Ph.D. |publisher=University of Toronto |accessdate=26 December 2016}}</ref> This sgRNA can be joined together with the Cas9 gene and made into a plasmid in order to be transfected into cells. |
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[[File:CRISPR transfection.png|thumb|373x373px|Overview of the transfection and DNA cleaving by CRISPR Cas9 (crRNA and tracrRNA are often joined as one strand of RNA when designing a plasmid)<ref name="Ran_2013" />]] |
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==== Structure ==== |
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CRISPR/Cas9 offers a high degree of fidelity and relatively simple construction. It depends on two factors for its specificity: the target sequence and the PAM. The target sequence is 20 bases long as part of each CRISPR locus in the crRNA array.<ref name="Ran_2013">{{cite journal | vauthors = Ran FA, Hsu PD, Wright J, Agarwala V, Scott DA, Zhang F | title = Genome engineering using the CRISPR-Cas9 system | journal = Nature Protocols | volume = 8 | issue = 11 | pages = 2281–308 | date = November 2013 | pmid = 24157548 | pmc = 3969860 | doi = 10.1038/nprot.2013.143 }}</ref> A typical crRNA array has multiple unique target sequences. Cas9 proteins select the correct location on the host's genome by utilizing the sequence to bond with base pairs on the host DNA. The sequence is not part of the Cas9 protein and as a result is customizable and can be independently [[Oligonucleotide synthesis|synthesized]].<ref>{{cite journal | vauthors = Horvath P, Barrangou R | title = CRISPR/Cas, the immune system of bacteria and archaea | journal = Science | volume = 327 | issue = 5962 | pages = 167–70 | date = January 2010 | pmid = 20056882 | doi = 10.1126/science.1179555 }}</ref><ref>{{cite journal | vauthors = Bialk P, Rivera-Torres N, Strouse B, Kmiec EB | title = Regulation of Gene Editing Activity Directed by Single-Stranded Oligonucleotides and CRISPR/Cas9 Systems | journal = PLOS One | volume = 10 | issue = 6 | pages = e0129308 | date = 2015-06-08 | pmid = 26053390 | pmc = 4459703 | doi = 10.1371/journal.pone.0129308 }}</ref> |
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The PAM sequence on the host genome is recognized by Cas9. Cas9 cannot be easily modified to recognize a different PAM sequence. However this is not too limiting as it is a short sequence and nonspecific (e.g. the SpCas9 PAM sequence is 5'-NGG-3' and in the human genome occurs roughly every 8 to 12 base pairs).<ref name="Ran_2013" /> |
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Once these have been assembled into a plasmid and transfected into cells the Cas9 protein with the help of the crRNA finds the correct sequence in the host cell's DNA and – depending on the Cas9 variant – creates a single or double strand break in the DNA.<ref>{{cite web |url=http://news.berkeley.edu/2015/11/12/crispr-cas9-gene-editing-check-three-times-cut-once/ |title=CRISPR-Cas9 gene editing: check three times, cut once |author=Robert Sanders |date=12 November 2015 |publisher=University of California, Berkeley |accessdate=26 December 2016 |archiveurl=https://web.archive.org/web/20161226231842/http://news.berkeley.edu/2015/11/12/crispr-cas9-gene-editing-check-three-times-cut-once/ |archivedate=26 December 2016 |deadurl=no}}</ref> |
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Properly spaced single strand breaks in the host DNA can trigger [[homology directed repair]], which is less error prone than the non-homologous end joining that typically follows a double strand break. Providing a DNA repair template allows for the insertion of a specific DNA sequence at an exact location within the genome. The repair template should extend 40 to 90 base pairs beyond the Cas9 induced DNA break.<ref name="Ran_2013" /> The goal is for the cell's HDR process to utilize the provided repair template and thereby incorporate the new sequence into the genome. Once incorporated, this new sequence is now part of the cell's genetic material and passes into its daughter cells. |
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Many online tools are available to aid in designing effective sgRNA sequences.<ref>{{cite web|title = Optimized CRISPR Design|url = http://crispr.mit.edu/|website = crispr.mit.edu|accessdate = 2015-12-20}}</ref> |
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==== Delivery ==== |
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Scientists can use viral or non-viral systems for delivery of the Cas9 and sgRNA into target cells. [[Electroporation]] of DNA, RNA or ribonucleocomplexes is the most common and cheapest system. This technique was used to edit [[CXCR4]] and [[Programmed cell death protein 1|PD-1]], knocking in new sequences to replace specific genetic "letters" in these proteins. The group was then able to sort the cells, using cell surface markers, to help identify successfully edited cells.<ref>{{cite web|title = Scientists successfully edit human immune-system T cells {{!}} KurzweilAI|url = http://www.kurzweilai.net/scientists-successfully-edit-human-immune-system-t-cells|website = www.kurzweilai.net|accessdate = 2016-01-01}}</ref> Deep sequencing of a target site confirmed that knock-in genome modifications had occurred with up to ∼20% efficiency, which accounted for up to approximately one-third of total editing events.<ref>{{cite journal | vauthors = Schumann K, Lin S, Boyer E, Simeonov DR, Subramaniam M, Gate RE, Haliburton GE, Ye CJ, Bluestone JA, Doudna JA, Marson A | title = Generation of knock-in primary human T cells using Cas9 ribonucleoproteins | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 112 | issue = 33 | pages = 10437–42 | date = August 2015 | pmid = 26216948 | pmc = 4547290 | doi = 10.1073/pnas.1512503112 }}</ref> However, hard-to-transfect cells (stem cells, neurons, hematopoietic cells, etc.) require more efficient delivery systems such as those based on [[lentivirus]] (LVs), [[Adenoviridae|adenovirus]] (AdV) and [[adeno-associated virus]] (AAV). |
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==== Editing ==== |
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CRISPRs have been used to cut five<ref name=craze/> to 62 genes at once: pig cells have been engineered to inactivate all 62 [[Porcine endogenous retroviruses|Porcine Endogenous Retroviruses]] in the pig genome, which eliminated transinfection from the pig to human cells in culture.<ref>{{cite news | newspaper=NY Times | url=https://www.nytimes.com/2015/10/20/science/editing-of-pig-dna-may-lead-to-more-organs-for-people.html?_r=1 | first = Carl | last = Zimmerman | name-list-format = vanc | title=Editing of Pig DNA May Lead to More Organs for People | date=Oct 15, 2015}}</ref> CRISPR's low cost compared to alternatives is widely seen as revolutionary.<ref name="nature99">{{cite journal |doi=10.1038/522020a |pmid=26040877 |title=CRISPR, the disruptor |journal=Nature |volume=522 |issue=7554 |pages=20–4 |year=2015 |last1=Ledford |first1=Heidi | name-list-format = vanc | bibcode=2015Natur.522...20L }}</ref><ref name="vb99">{{cite web|url = http://news.vanderbilt.edu/2014/08/new-technique-accelerates-genome-editing-process/|title = New technique accelerates genome editing process|date = 21 August 2014|accessdate = |website = research news @ Vanderbilt|publisher = Vanderbilt University|last = Snyder|first = Bill | name-list-format = vanc | location = Nashville, Tennessee}}</ref> |
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Selective engineered redirection of the CRISPR/Cas system was first demonstrated in 2012 in:<ref name=halemajumder2012>{{cite journal | vauthors = Hale CR, Majumdar S, Elmore J, Pfister N, Compton M, Olson S, Resch AM, Glover CV, Graveley BR, Terns RM, Terns MP | title = Essential features and rational design of CRISPR RNAs that function with the Cas RAMP module complex to cleave RNAs | journal = Molecular Cell | volume = 45 | issue = 3 | pages = 292–302 | date = February 2012 | pmid = 22227116 | pmc = 3278580 | doi = 10.1016/j.molcel.2011.10.023 }}</ref><ref name="pmid18157154">{{cite journal | vauthors = Sorek R, Kunin V, Hugenholtz P | title = CRISPR--a widespread system that provides acquired resistance against phages in bacteria and archaea | journal = Nature Reviews Microbiology | volume = 6 | issue = 3 | pages = 181–6 | date = March 2008 | pmid = 18157154 | pmc = | doi = 10.1038/nrmicro1793 }}</ref> |
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* Immunization of industrially important bacteria, including some used in food production and large-scale fermentation |
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* Cellular or organism RNA-guided [[genome engineering]]. Proof of concept studies demonstrated examples both ''[[in vitro]]''<ref name=pmid26121415/><ref name="pmid22745249">{{cite journal | vauthors = Jinek M, Chylinski K, Fonfara I, Hauer M, Doudna JA, Charpentier E | title = A programmable dual-RNA-guided DNA endonuclease in adaptive bacterial immunity | journal = Science | volume = 337 | issue = 6096 | pages = 816–21 | date = August 2012 | pmid = 22745249 | pmc = | doi = 10.1126/science.1225829 | bibcode = 2012Sci...337..816J }}</ref><ref name="pmid22949671"/> and ''[[in vivo]]''<ref name="pmid23643243"/><ref>{{cite journal | vauthors = Cong L, Ran FA, Cox D, Lin S, Barretto R, Habib N, Hsu PD, Wu X, Jiang W, Marraffini LA, Zhang F | title = Multiplex genome engineering using CRISPR/Cas systems | journal = Science | volume = 339 | issue = 6121 | pages = 819–23 | date = February 2013 | pmid = 23287718 | pmc = 3795411 | doi = 10.1126/science.1231143 | bibcode = 2013Sci...339..819C }}</ref><ref>{{cite journal | vauthors = Mali P, Yang L, Esvelt KM, Aach J, Guell M, DiCarlo JE, Norville JE, Church GM | title = RNA-guided human genome engineering via Cas9 | journal = Science | volume = 339 | issue = 6121 | pages = 823–6 | date = February 2013 | pmid = 23287722 | pmc = 3712628 | doi = 10.1126/science.1232033 | bibcode = 2013Sci...339..823M }}<br/>{{cite journal | vauthors = Hou Z, Zhang Y, Propson NE, Howden SE, Chu LF, Sontheimer EJ, Thomson JA | title = Efficient genome engineering in human pluripotent stem cells using Cas9 from Neisseria meningitidis | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 110 | issue = 39 | pages = 15644–9 | date = September 2013 | pmid = 23940360| pmc = 3785731| doi = 10.1073/pnas.1313587110 | bibcode = 2013PNAS..11015644H }}</ref> |
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==== Controlled genome editing ==== |
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Several variants of CRISPR/Cas9 allow gene activation or genome editing with an external trigger such as light or small molecules.<ref name=":1">{{cite journal | vauthors = Oakes BL, Nadler DC, Flamholz A, Fellmann C, Staahl BT, Doudna JA, Savage DF | title = Profiling of engineering hotspots identifies an allosteric CRISPR-Cas9 switch | journal = Nature Biotechnology | volume = 34 | issue = 6 | pages = 646–51 | date = June 2016 | pmid = 27136077 | pmc = 4900928 | doi = 10.1038/nbt.3528 }}</ref><ref name="pmid26857072">{{cite journal | vauthors = Nuñez JK, Harrington LB, Doudna JA | title = Chemical and Biophysical Modulation of Cas9 for Tunable Genome Engineering | journal = ACS Chemical Biology | volume = 11 | issue = 3 | pages = 681–8 | date = March 2016 | pmid = 26857072 | doi = 10.1021/acschembio.5b01019 }}</ref><ref name="pmid26996256">{{cite journal | vauthors = Zhou W, Deiters A | title = Conditional Control of CRISPR/Cas9 Function | journal = Angewandte Chemie | volume = 55 | issue = 18 | pages = 5394–9 | date = April 2016 | pmid = 26996256 | doi = 10.1002/anie.201511441 }}</ref> These include photoactivatable CRISPR systems developed by fusing light-responsive protein partners with an activator domain and a dCas9 for gene activation,<ref name="pmid25664691">{{cite journal | vauthors = Polstein LR, Gersbach CA | title = A light-inducible CRISPR-Cas9 system for control of endogenous gene activation | journal = Nature Chemical Biology | volume = 11 | issue = 3 | pages = 198–200 | date = March 2015 | pmid = 25664691 | pmc = 4412021 | doi = 10.1038/nchembio.1753 }}</ref><ref name="pmid25619936">{{cite journal | vauthors = Nihongaki Y, Yamamoto S, Kawano F, Suzuki H, Sato M | title = CRISPR-Cas9-based photoactivatable transcription system | journal = Chemistry & Biology | volume = 22 | issue = 2 | pages = 169–74 | date = February 2015 | pmid = 25619936 | doi = 10.1016/j.chembiol.2014.12.011 }}</ref> or fusing similar light responsive domains with two constructs of split-Cas9,<ref name="pmid25713377">{{cite journal | vauthors = Wright AV, Sternberg SH, Taylor DW, Staahl BT, Bardales JA, Kornfeld JE, Doudna JA | title = Rational design of a split-Cas9 enzyme complex | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 112 | issue = 10 | pages = 2984–9 | date = March 2015 | pmid = 25713377 | pmc = 4364227 | doi = 10.1073/pnas.1501698112 }}</ref><ref name="pmid26076431">{{cite journal | vauthors = Nihongaki Y, Kawano F, Nakajima T, Sato M | title = Photoactivatable CRISPR-Cas9 for optogenetic genome editing | journal = Nature Biotechnology | volume = 33 | issue = 7 | pages = 755–60 | date = July 2015 | pmid = 26076431 | doi = 10.1038/nbt.3245 }}</ref> or by incorporating caged unnatural amino acids into Cas9,<ref name="pmid25905628">{{cite journal | vauthors = Hemphill J, Borchardt EK, Brown K, Asokan A, Deiters A | title = Optical Control of CRISPR/Cas9 Gene Editing | journal = Journal of the American Chemical Society | volume = 137 | issue = 17 | pages = 5642–5 | date = May 2015 | pmid = 25905628 | pmc = 4919123 | doi = 10.1021/ja512664v }}</ref> or by modifying the guide RNAs with photocleavable complements for genome editing.<ref name="pmid27554600">{{cite journal | vauthors = Jain PK, Ramanan V, Schepers AG, Dalvie NS, Panda A, Fleming HE, Bhatia SN | title = Development of Light-Activated CRISPR Using Guide RNAs with Photocleavable Protectors | journal = Angewandte Chemie | volume = 55 | issue = 40 | pages = 12440–4 | date = September 2016 | pmid = 27554600 | doi = 10.1002/anie.201606123 }}</ref> |
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Methods to control genome editing with small molecules include an allosteric Cas9, with no detectable background editing, that will activate binding and cleavage upon the addition of [[Afimoxifene|4-hydroxytamoxifen]] (4-HT),<ref name=":1" /> 4-HT responsive [[intein]]-linked Cas9s<ref>{{cite journal | vauthors = Davis KM, Pattanayak V, Thompson DB, Zuris JA, Liu DR | title = Small molecule-triggered Cas9 protein with improved genome-editing specificity | journal = Nature Chemical Biology | volume = 11 | issue = 5 | pages = 316–8 | date = May 2015 | pmid = 25848930 | pmc = 4402137 | doi = 10.1038/nchembio.1793 }}</ref> or a Cas9 that is 4-HT responsive when fused to four ERT2 domains.<ref>{{cite journal | vauthors = Liu KI, Ramli MN, Woo CW, Wang Y, Zhao T, Zhang X, Yim GR, Chong BY, Gowher A, Chua MZ, Jung J, Lee JH, Tan MH | title = A chemical-inducible CRISPR-Cas9 system for rapid control of genome editing | journal = Nature Chemical Biology | volume = 12 | issue = 11 | pages = 980–987 | date = November 2016 | pmid = 27618190 | doi = 10.1038/nchembio.2179 }}</ref> Intein-inducible split-Cas9 allows [[dimerization (chemistry)|dimerization]] of Cas9 fragments<ref>{{cite journal | vauthors = Truong DJ, Kühner K, Kühn R, Werfel S, Engelhardt S, Wurst W, Ortiz O | title = Development of an intein-mediated split-Cas9 system for gene therapy | journal = Nucleic Acids Research | volume = 43 | issue = 13 | pages = 6450–8 | date = July 2015 | pmid = 26082496 | pmc = 4513872 | doi = 10.1093/nar/gkv601 }}</ref> and [[Sirolimus|Rapamycin]]-inducible split-Cas9 system developed by fusing two constructs of split Cas9 with FRB and [[FKBP]] fragments.<ref>{{cite journal | vauthors = Zetsche B, Volz SE, Zhang F | title = A split-Cas9 architecture for inducible genome editing and transcription modulation | journal = Nature Biotechnology | volume = 33 | issue = 2 | pages = 139–42 | date = February 2015 | pmid = 25643054 | pmc = 4503468 | doi = 10.1038/nbt.3149 }}</ref> Furthermore, other studies have shown to induce transcription of Cas9 with a small molecule, [[Doxycycline|doxycyline]].<ref>{{cite journal | vauthors = González F, Zhu Z, Shi ZD, Lelli K, Verma N, Li QV, Huangfu D | title = An iCRISPR platform for rapid, multiplexable, and inducible genome editing in human pluripotent stem cells | journal = Cell Stem Cell | volume = 15 | issue = 2 | pages = 215–26 | date = August 2014 | pmid = 24931489 | pmc = 4127112 | doi = 10.1016/j.stem.2014.05.018 }}</ref><ref>{{cite journal | vauthors = Dow LE, Fisher J, O'Rourke KP, Muley A, Kastenhuber ER, Livshits G, Tschaharganeh DF, Socci ND, Lowe SW | title = Inducible in vivo genome editing with CRISPR-Cas9 | journal = Nature Biotechnology | volume = 33 | issue = 4 | pages = 390–4 | date = April 2015 | pmid = 25690852 | pmc = 4390466 | doi = 10.1038/nbt.3155 }}</ref> Small molecules can also be used to improve Homology Directed Repair (HDR),<ref>{{cite journal | vauthors = Yu C, Liu Y, Ma T, Liu K, Xu S, Zhang Y, Liu H, La Russa M, Xie M, Ding S, Qi LS | title = Small molecules enhance CRISPR genome editing in pluripotent stem cells | journal = Cell Stem Cell | volume = 16 | issue = 2 | pages = 142–7 | date = February 2015 | pmid = 25658371 | pmc = 4461869 | doi = 10.1016/j.stem.2015.01.003 }}</ref> often by inhibiting the Non-Homologous End Joining (NHEJ) pathway.<ref>{{cite journal | vauthors = Maruyama T, Dougan SK, Truttmann MC, Bilate AM, Ingram JR, Ploegh HL | title = Increasing the efficiency of precise genome editing with CRISPR-Cas9 by inhibition of nonhomologous end joining | journal = Nature Biotechnology | volume = 33 | issue = 5 | pages = 538–42 | date = May 2015 | pmid = 25798939 | pmc = 4618510 | doi = 10.1038/nbt.3190 }}</ref> These systems allow conditional control of CRISPR activity for improved precision, efficiency and spatiotemporal control. |
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In 2017, researchers successfully used CRISPR-Cas9 as a treatment in a mouse model of human genetic deafness, by genetically editing the DNA in some cells in the ears of live mice.<ref name="GaoTao2017">{{cite journal | vauthors = Gao X, Tao Y, Lamas V, Huang M, Yeh WH, Pan B, Hu YJ, Hu JH, Thompson DB, Shu Y, Li Y, Wang H, Yang S, Xu Q, Polley DB, Liberman MC, Kong WJ, Holt JR, Chen ZY, Liu DR | display-authors = 6 | title = Treatment of autosomal dominant hearing loss by in vivo delivery of genome editing agents | journal = Nature | date = December 2017 | pmid = 29258297 | doi = 10.1038/nature25164 | volume=553 | issue = 7687 | pmc=5784267 | pages=217–221}}</ref> |
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=== Knockdown/activation === |
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{{main|CRISPR interference}} |
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[[File:Dead-Cas9 potential applications.png|thumb|416x416px]] |
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Using "dead" versions of Cas9 ([[Cas9#Interference of transcription by dCas9|dCas9]]) eliminates CRISPR's DNA-cutting ability, while preserving its ability to target desirable sequences. Multiple groups added various regulatory factors to dCas9s, enabling them to turn almost any gene on or off or adjust its level of activity.<ref name="Science_Breakthrough">{{cite web | title = And Science's Breakthrough of the Year is ...|url = http://news.sciencemag.org/scientific-community/2015/12/and-science-s-breakthrough-year|website = news.sciencemag.org|accessdate = 2015-12-21|date = December 17, 2015|last = Science News Staff}}</ref> Like RNAi, CRISPR interference (CRISPRi) turns off genes in a reversible fashion by targeting, but not cutting a site. The targeted site is methylated, [[Epigenetics|epigenetically]] modifying the gene. This modification inhibits transcription. Conversely, CRISPR-mediated activation (CRISPRa) promotes gene transcription.<ref>{{cite journal | vauthors = Dominguez AA, Lim WA, Qi LS | title = Beyond editing: repurposing CRISPR-Cas9 for precision genome regulation and interrogation | journal = Nature Reviews Molecular Cell Biology | volume = 17 | issue = 1 | pages = 5–15 | date = January 2016 | pmid = 26670017 | pmc = 4922510 | doi = 10.1038/nrm.2015.2 }}</ref> Cas9 is an effective way of targeting and silencing specific genes at the DNA level.<ref name="pmid24336571">{{cite journal | vauthors = Shalem O, Sanjana NE, Hartenian E, Shi X, Scott DA, Mikkelsen TS, Heckl D, Ebert BL, Root DE, Doench JG, Zhang F | title = Genome-scale CRISPR-Cas9 knockout screening in human cells | journal = Science | volume = 343 | issue = 6166 | pages = 84–7 | date = January 2014 | pmid = 24336571 | pmc = 4089965 | doi = 10.1126/science.1247005 }}</ref> In bacteria, the presence of Cas9 alone is enough to block transcription. For mammalian applications, a section of protein is added. Its guide RNA targets regulatory DNA sequences called [[Promoter (genetics)|promoters]] that immediately precede the target gene.<ref name=craze/> |
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Cas9 was used to carry synthetic [[transcription factor]]s that activated specific human genes. The technique achieved a strong effect by targeting multiple CRISPR constructs to slightly different locations on the gene's promoter.<ref name=craze/> |
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=== RNA editing === |
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In 2016 researchers demonstrated that CRISPR from an ordinary mouth bacterium could be used to edit [[RNA]]. The researchers searched databases containing hundreds of millions of genetic sequences for those that resembled Crispr genes. They considered the [[fusobacteria]] ''Leptotrichia shahii''. It had a group of genes that resembled CRISPR genes, but with important differences. When the researchers equipped other bacteria with these genes, which they called C2c2, they found that the organisms gained a novel defense.<ref name="Zimmer_2016">{{cite news | url = https://www.nytimes.com/2016/06/04/science/rna-c2c2-gene-editing-dna-crispr.html | title = Scientists Find Form of Crispr Gene Editing With New Capabilities|last=Zimmer|first=Carl | name-list-format = vanc | date=2016-06-03|newspaper=The New York Times|issn=0362-4331|access-date=2016-06-10}}</ref> |
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Many viruses encode their genetic information in RNA rather than DNA that they repurpose to make new viruses. [[HIV]] and [[poliovirus]] are such viruses. Bacteria with C2c2 make molecules that can dismember RNA, destroying the virus. Tailoring these genes opened any RNA molecule to editing.<ref name="Zimmer_2016" /> |
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CRISPR-Cas systems can also be employed for editing of [[MicroRNA|micro-RNA]] and [[Long non-coding RNA|long-noncoding RNA]] genes in plants.<ref>{{cite journal | vauthors = Basak J, Nithin C | title = Targeting Non-Coding RNAs in Plants with the CRISPR-Cas Technology is a Challenge yet Worth Accepting | journal = Frontiers in Plant Science | volume = 6 | pages = 1001 | date = 2015 | pmid = 26635829 | doi = 10.3389/fpls.2015.01001 }}</ref> |
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=== Disease models === |
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CRISPR simplifies creation of [[Genetically modified organism#Mammals|animals for research]] that mimic disease or show what happens when a gene is [[Gene knockdown|knocked down]] or mutated. CRISPR may be used at the [[germline]] level to create animals where the gene is changed everywhere, or it may be targeted at non-germline cells.<ref name="pmid25914022">{{cite journal | vauthors = van Erp PB, Bloomer G, Wilkinson R, Wiedenheft B | title = The history and market impact of CRISPR RNA-guided nucleases | journal = Current Opinion in Virology | volume = 12 | issue = | pages = 85–90 | date = June 2015 | pmid = 25914022 | doi = 10.1016/j.coviro.2015.03.011 | pmc = 4470805}}</ref><ref name="pmid25819765">{{cite journal | vauthors = Maggio I, Gonçalves MA | title = Genome editing at the crossroads of delivery, specificity, and fidelity | journal = Trends in Biotechnology | volume = 33 | issue = 5 | pages = 280–91 | date = May 2015 | pmid = 25819765 | doi = 10.1016/j.tibtech.2015.02.011 }}</ref><ref name="pmid25868999">{{cite journal | vauthors = Rath D, Amlinger L, Rath A, Lundgren M | title = The CRISPR-Cas immune system: biology, mechanisms and applications | journal = Biochimie | volume = 117 | issue = | pages = 119–28 | date = October 2015 | pmid = 25868999 | doi = 10.1016/j.biochi.2015.03.025 }}</ref> |
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CRISPR can be utilized to create human cellular models of disease. For instance, applied to human [[Cell potency|pluripotent stem cells]] CRISPR introduced targeted mutations in genes relevant to [[polycystic kidney disease]] (PKD) and [[focal segmental glomerulosclerosis]] (FSGS).<ref name="ReferenceA">{{cite journal | vauthors = Freedman BS, Brooks CR, Lam AQ, Fu H, Morizane R, Agrawal V, Saad AF, Li MK, Hughes MR, Werff RV, Peters DT, Lu J, Baccei A, Siedlecki AM, Valerius MT, Musunuru K, McNagny KM, Steinman TI, Zhou J, Lerou PH, Bonventre JV | display-authors = 6 | title = Modelling kidney disease with CRISPR-mutant kidney organoids derived from human pluripotent epiblast spheroids | journal = Nature Communications | volume = 6 | pages = 8715 | date = October 2015 | pmid = 26493500 | pmc = 4620584 | doi = 10.1038/ncomms9715 }}</ref> These CRISPR-modified pluripotent stem cells were subsequently grown into human kidney [[organoid]]s that exhibited disease-specific phenotypes. Kidney [[organoid]]s from stem cells with PKD mutations formed large, translucent cyst structures from kidney tubules. The cysts were capable of reaching macroscopic dimensions, up to one centimeter in diameter.<ref>{{cite journal | vauthors = Cruz NM, Song X, Czerniecki SM, Gulieva RE, Churchill AJ, Kim YK, Winston K, Tran LM, Diaz MA, Fu H, Finn LS, Pei Y, Himmelfarb J, Freedman BS | display-authors = 6 | title = Organoid cystogenesis reveals a critical role of microenvironment in human polycystic kidney disease | journal = Nature Materials | volume = 16 | issue = 11 | pages = 1112–1119 | date = November 2017 | pmid = 28967916 | doi = 10.1038/nmat4994 }}</ref> Kidney organoids with mutations in a gene linked to FSGS developed junctional defects between [[podocyte]]s, the filtering cells affected in that disease. This was traced to the inability of podocytes ability to form microvilli between adjacent cells.<ref>{{cite journal | vauthors = Kim YK, Refaeli I, Brooks CR, Jing P, Gulieva RE, Hughes MR, Cruz NM, Liu Y, Churchill AJ, Wang Y, Fu H, Pippin JW, Lin LY, Shankland SJ, Vogl AW, McNagny KM, Freedman BS | display-authors = 6 | title = Gene-Edited Human Kidney Organoids Reveal Mechanisms of Disease in Podocyte Development | journal = Stem Cells | volume = 35 | issue = 12 | pages = 2366–2378 | date = December 2017 | pmid = 28905451 | doi = 10.1002/stem.2707 | pmc=5742857}}</ref> Importantly, these disease phenotypes were absent in control organoids of identical genetic background, but lacking the CRISPR modifications.<ref name="ReferenceA"/> |
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A similar approach was taken to model long QT syndrome in [[Cardiac muscle cell|cardiomyocytes]] derived from pluripotent stem cells.<ref>{{cite journal | vauthors = Bellin M, Casini S, Davis RP, D'Aniello C, Haas J, Ward-van Oostwaard D, Tertoolen LG, Jung CB, Elliott DA, Welling A, Laugwitz KL, Moretti A, Mummery CL | title = Isogenic human pluripotent stem cell pairs reveal the role of a KCNH2 mutation in long-QT syndrome | journal = The EMBO Journal | volume = 32 | issue = 24 | pages = 3161–75 | date = December 2013 | pmid = 24213244 | pmc = 3981141 | doi = 10.1038/emboj.2013.240 }}</ref> These CRISPR-generated cellular models, with isogenic controls, provide a new way to study human disease and test drugs. |
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=== Gene drive === |
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{{Main|Gene drive}} |
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Gene drives may provide a powerful tool to restore balance of ecosystems by eliminating invasive species. Concerns regarding efficacy, unintended consequences in the target species as well as non-target species have been raised particularly in the potential for accidental release from laboratories into the wild. Scientists have proposed several safeguards for ensuring the containment of experimental gene drives including molecular, reproductive, and ecological.<ref>{{cite journal | vauthors = Akbari OS, Bellen HJ, Bier E, Bullock SL, Burt A, Church GM, Cook KR, Duchek P, Edwards OR, Esvelt KM, Gantz VM, Golic KG, Gratz SJ, Harrison MM, Hayes KR, James AA, Kaufman TC, Knoblich J, Malik HS, Matthews KA, O'Connor-Giles KM, Parks AL, Perrimon N, Port F, Russell S, Ueda R, Wildonger J | display-authors = 6 | title = BIOSAFETY. Safeguarding gene drive experiments in the laboratory | journal = Science | volume = 349 | issue = 6251 | pages = 927–9 | date = August 2015 | pmid = 26229113 | pmc = 4692367 | doi = 10.1126/science.aac7932 | bibcode = 2015Sci...349..927A }}</ref> Many recommend that immunization and reversal drives be developed in tandem with gene drives in order to overwrite their effects if necessary.<ref>{{cite journal | vauthors = Caplan AL, Parent B, Shen M, Plunkett C | title = No time to waste--the ethical challenges created by CRISPR: CRISPR/Cas, being an efficient, simple, and cheap technology to edit the genome of any organism, raises many ethical and regulatory issues beyond the use to manipulate human germ line cells | journal = EMBO Reports | volume = 16 | issue = 11 | pages = 1421–6 | date = November 2015 | pmid = 26450575 | pmc = 4641494 | doi = 10.15252/embr.201541337 }}</ref> There remains consensus that long-term effects must be studied more thoroughly particularly in the potential for ecological disruption that cannot be corrected with reversal drives.<ref>{{cite journal | vauthors = Oye KA, Esvelt K, Appleton E, Catteruccia F, Church G, Kuiken T, Lightfoot SB, McNamara J, Smidler A, Collins JP | display-authors = 6 | title = Biotechnology. Regulating gene drives | journal = Science | volume = 345 | issue = 6197 | pages = 626–8 | date = August 2014 | pmid = 25035410 | doi = 10.1126/science.1254287 | bibcode = 2014Sci...345..626O }}</ref> |
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=== Biomedicine === |
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CRISPR/Cas-based "RNA-guided nucleases" can be used to target [[virulence factors]], genes encoding [[antibiotic resistance]] and other medically relevant sequences of interest. This technology thus represents a novel form of antimicrobial therapy and a strategy by which to manipulate bacterial populations.<ref name="Gomaaetal2014">{{cite journal | vauthors = Gomaa AA, Klumpe HE, Luo ML, Selle K, Barrangou R, Beisel CL| title = Programmable removal of bacterial strains by use of genome-targeting CRISPR-Cas systems | journal = MBio | volume = 5 | issue = 1 | pages = e00928–13 | date = January 2014 | pmid = 24473129 | pmc = 3903277 | doi = 10.1128/mBio.00928-13 }}</ref><ref name="CitorikMimee2014">{{cite journal | vauthors = Citorik RJ, Mimee M, Lu TK | title = Sequence-specific antimicrobials using efficiently delivered RNA-guided nucleases | journal = Nature Biotechnology | volume = 32 | issue = 11 | pages = 1141–5 | date = November 2014 | pmid = 25240928 | pmc = 4237163 | doi = 10.1038/nbt.3011 }}</ref> Recent studies suggested a correlation between the interfering of the CRISPR/Cas locus and acquisition of antibiotic resistance<ref name="Gholizadeh2017">{{cite journal | vauthors = Gholizadeh P, Aghazadeh M, Asgharzadeh M, Kafil HS,| title = Suppressing the CRISPR/Cas adaptive immune system in bacterial infections | journal = European Journal of Clinical Microbiology & Infectious Diseases | volume = 36 | issue = 11 | pages = 2043–2051 | date = October 2017 | pmid = 28601970 | doi = 10.1007/s10096-017-3036-2 }}</ref> This system provides protection of bacteria against invading foreign DNA, such as transposons, bacteriophages and plasmids. This system was shown to be a strong selective pressure for the acquisition of antibiotic resistance and virulence factor in bacterial pathogens.<ref name="Gholizadeh2017" /> Some of the affected genes are tied to human diseases, including those involved in muscle differentiation, cancer, inflammation and fetal [[hemoglobin]].<ref name="craze" /> |
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Research suggests that CRISPR is an effective way to limit replication of multiple [[herpesviruses]]. It was able to eradicate viral DNA in the case of [[Epstein-Barr virus]] (EBV). Anti-herpesvirus CRISPRs have promising applications such as removing cancer-causing EBV from tumor cells, helping rid donated organs for [[immunocompromised]] patients of viral invaders, or preventing [[Herpes labialis|cold sore]] outbreaks and recurrent eye infections by blocking [[HSV-1]] reactivation. As of August 2016, these were awaiting testing.<ref name="pmid27362483">{{cite journal | vauthors = van Diemen FR, Kruse EM, Hooykaas MJ, Bruggeling CE, Schürch AC, van Ham PM, Imhof SM, Nijhuis M, Wiertz EJ, Lebbink RJ | title = CRISPR/Cas9-Mediated Genome Editing of Herpesviruses Limits Productive and Latent Infections | journal = PLoS Pathogens | volume = 12 | issue = 6 | pages = e1005701 | year = 2016 | pmid = 27362483 | pmc = 4928872 | doi = 10.1371/journal.ppat.1005701 | laysummary = https://www.youtube.com/watch?v=lQaWh8VLkiU&feature=youtu.be | laysource = PLOS Media YouTube Channel }}</ref> CRISPR is being applied to develop tissue-based treatments for cancer and other diseases.<ref name="Science_Breakthrough" /><ref name="pmid27595406">{{cite journal | vauthors = Liu Y, Zhan Y, Chen Z, He A, Li J, Wu H, Liu L, Zhuang C, Lin J, Guo X, Zhang Q, Huang W, Cai Z | title = Directing cellular information flow via CRISPR signal conductors | journal = Nature Methods | volume = 13| issue = 11| date = September 2016 | pmid = 27595406 | doi = 10.1038/nmeth.3994 | pages=938–944}}</ref> |
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CRISPR may revive the concept of [[Xenotransplantation|transplanting]] animal organs into people. [[Retroviruses]] present in animal genomes could harm transplant recipients. In 2015 a team eliminated 62 copies of a retrovirus's DNA from the pig genome in a kidney epithelial cell.<ref name="Science_Breakthrough"/> Researchers recently demonstrated the ability to birth live pig specimens after removing these retroviruses from their genome using CRISPR for the first time.<ref>{{Cite news|url=https://www.technologyreview.com/s/608579/crispr-opens-up-new-possibilities-for-transplants-using-pig-organs/|title=Using CRISPR on pigs could make their organs safer for human transplant|last=Mullin|first=Emily | name-list-format = vanc |work=MIT Technology Review|access-date=2017-09-09}}</ref> |
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CRISPR may have applications in tissue engineering and regenerative medicine, such as by creating human blood vessels that lack expression of [[MHC class II]] proteins, which often cause transplant rejection.<ref>{{cite journal | vauthors = Abrahimi P, Chang WG, Kluger MS, Qyang Y, Tellides G, Saltzman WM, Pober JS | title = Efficient gene disruption in cultured primary human endothelial cells by CRISPR/Cas9 | journal = Circulation Research | volume = 117 | issue = 2 | pages = 121–8 | date = July 2015 | pmid = 25940550 | pmc = 4490936 | doi = 10.1161/CIRCRESAHA.117.306290 }}</ref> |
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==== CRISPR in Cancer ==== |
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As of 2016 CRISPR had been studied in animal models and cancer cell lines, to learn if it can be used to repair or thwart mutated genes that cause [[cancer]].<ref>{{cite journal | vauthors = Khan FA, Pandupuspitasari NS, Chun-Jie H, Ao Z, Jamal M, Zohaib A, Khan FA, Hakim MR, ShuJun Z | title = CRISPR/Cas9 therapeutics: a cure for cancer and other genetic diseases | journal = Oncotarget | volume = 7 | issue = 32 | pages = 52541–52552 | date = August 2016 | pmid = 27250031 | pmc = 5239572 | doi = 10.18632/oncotarget.9646 }}</ref> |
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The first clinical trial involving CRISPR started in 2016. It involved removing immune cells from people with lung cancer, using CRISPR to edit out the gene expressed PD-1, then administrating the altered cells back to the same person. 20 other trials were under way or nearly ready, mostly in China, as of 2017.<ref>{{cite news | first = Michael | last = Le Page | name-list-format = vanc | title=Boom in human gene editing as 20 CRISPR trials gear up|url=https://www.newscientist.com/article/2133095-boom-in-human-gene-editing-as-20-crispr-trials-gear-up/|work=New Scientist|date=7 June 2017}}</ref> |
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In 2016 the [[Food and Drug Administration|United States Food and Drug Administration]] (FDA) approved a clinical trial in which CRISPR would be used to alter T cells extracted from people with different kinds of cancer and then administer those engineered T cells back to the same people.<ref>{{cite journal |doi=10.1038/nature.2016.20137 |title=First CRISPR clinical trial gets green light from US panel |journal=Nature |year=2016 |last1=Reardon |first1=Sara | name-list-format = vanc }}</ref> |
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=== Gene function === |
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In 2015, multiple studies attempted to systematically disable each individual human gene, in an attempt to identify which genes were essential to human biology. Between 1,600 and 1,800 genes passed this test—of the 20,000 or so known human genes. Such genes are more strongly activated, and unlikely to carry disabling mutations. They are more likely to have indispensable counterparts in other species. They build proteins that unite to form larger collaborative complexes. The studies also cataloged the essential genes in four cancer-cell lines and identified genes that are expendable in healthy cells, but crucial in specific tumor types and drugs that could target these rogue genes.<ref>{{cite web|title = The Revolutionary Gene-Editing Technique That Reveals Cancer's Weaknesses|url = https://www.theatlantic.com/science/archive/2015/11/a-revolutionary-gene-editing-technique-reveals-cancers-weaknesses/417495/|website = The Atlantic|access-date = 2016-02-21 | first = Ed | last = Yong | name-list-format = vanc | date = 2015-11-25}}</ref> |
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The specific functions of some 18 percent of the essential genes are unidentified. In one 2015 targeting experiment, disabling individual genes in groups of cells attempted to identify those involved in resistance to a [[melanoma]] drug. Each such gene manipulation is itself a separate "drug", potentially opening the entire genome to CRISPR-based regulation.<ref name="Science_Breakthrough" /> |
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In 2016-2017, a CRISPR/Cas-based approach to genetically engineering adult rodent brains ''in vivo'' was successfully demonstrated.<ref>{{cite journal | vauthors = Sandweiss AJ, McIntosh MI, Moutal A, Davidson-Knapp R, Hu J, Giri AK, Yamamoto T, Hruby VJ, Khanna R, Largent-Milnes TM, Vanderah TW | title = Genetic and pharmacological antagonism of NK1 receptor prevents opiate abuse potential | journal = Molecular Psychiatry | date = May 2017 | pmid = 28485408 | doi = 10.1038/mp.2017.102 | pmc=5680162}}</ref><ref>{{cite journal | vauthors = Staahl BT, Benekareddy M, Coulon-Bainier C, Banfal AA, Floor SN, Sabo JK, Urnes C, Munares GA, Ghosh A, Doudna JA | name-list-format = vanc | title = Efficient genome editing in the mouse brain by local delivery of engineered Cas9 ribonucleoprotein complexes | journal = Nature Biotechnology | volume = 35 | issue = 5 | pages = 431–434 | date = May 2017 | pmid = 28191903 | doi = 10.1038/nbt.3806 }}</ref> |
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=== ''In vitro'' genetic depletion === |
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Unenriched sequencing libraries often have abundant undesired sequences. Cas9 can specifically deplete the undesired sequences with double strand breakage with up to 99% efficiency and without significant [[Off-target genome editing|off-target effects]] as seen with [[restriction enzyme]]s. Treatment with Cas9 can deplete abundant rRNA while increasing pathogen sensitivity in RNA-seq libraries.<ref name="pmid26944702">{{cite journal | vauthors = Gu W, Crawford ED, O'Donovan BD, Wilson MR, Chow ED, Retallack H, DeRisi JL | title = Depletion of Abundant Sequences by Hybridization (DASH): using Cas9 to remove unwanted high-abundance species in sequencing libraries and molecular counting applications | journal = Genome Biology | volume = 17 | issue = | pages = 41 | date = March 2016 | pmid = 26944702 | pmc = 4778327 | doi = 10.1186/s13059-016-0904-5 }}</ref> |
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=== ''In vivo'' applications === |
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CRISPR/Cas-9 can be used to edit the DNA of organisms ''in vivo'' and entire chromosomes can be eliminated from an organism at any point in its development. Chromosomes that have been deleted ''in vivo'' are the Y chromosomes and X chromosomes of adult lab mice and human chromosomes 14 and 21, in embryonic stem cell lines and [[aneuploid]] mice respectively. This method might be useful for treating genetic aneuploid diseases such as [[Down Syndrome]] and [[intersex]] disorders.<ref name="pmid29178945">{{cite journal | vauthors = Zuo E, Huo X, Yao X, Hu X, Sun Y, Yin J, He B, Wang X, Shi L, Ping J, Wei Y, Ying W, Wei W, Liu W, Tang C, Li Y, Hu J, Yang H | display-authors = 6 | title = CRISPR/Cas9-mediated targeted chromosome elimination | journal = Genome Biology | volume = 18 | issue = 1 | pages = 224 | year = 2017 | pmid = 29178945 | pmc = 5701507 | doi = 10.1186/s13059-017-1354-4 | lay-summary = https://www.genomeweb.com/gene-silencinggene-editing/crispr-used-eliminate-targeted-chromosomes-new-study | lay-source= Genome Web }}</ref> |
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Successful ''in vivo'' genome editing using CRISPR/Cas9 has been shown in several model organisms, such as ''Arabidopsis'', ''Caenorhadbitis elegans'', ''Saccharomyces cerevisiae'' and ''Drosophila''.<ref name="ReferenceC"/><ref name="quadauxo"/><ref name="metaeng"/><ref name="test">{{cite journal | vauthors = Feng Z, Mao Y, Xu N, Zhang B, Wei P, Yang DL, Wang Z, Zhang Z, Zheng R, Yang L, Zeng L | year = 2014 | title = Multigeneration analysis reveals the inheritance, specificity, and patterns of CRISPR/Cas-induced gene modifications in ''Arabidopsis'' | url = | journal = Proceedings of the National Academy of Sciences | volume = 111 | issue = 12| pages = 4632–4637 | doi=10.1073/pnas.1400822111}}</ref><ref name = "Friedland_2013" /><ref name="Lin_2015">{{cite journal | vauthors = Lin S, Ewen-Campen B, Ni X, Housden BE, Perrimon N | title = In Vivo Transcriptional Activation Using CRISPR/Cas9 in Drosophila | journal = Genetics | volume = 201 | issue = 2 | pages = 433–42 | date = October 2015 | pmid = 26245833 | pmc = 4596659 | doi = 10.1534/genetics.115.181065 }}</ref> In ''Drosophila melanogaster'', a nuclease-dead Cas9 (dCas9) was confirmed to highly activate transcription in the target genes of Twist and Snail ''in vivo''.<ref name="Lin_2015" /> For Arabidopsis and C. elegans, experiments focused on CRISPR-Cas induced genome mutations that could be stably inherited by the progeny of these two species.<ref name="test" /><ref name = "Friedland_2013" /> |
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== Patents and commercialization == |
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As of December 2014, [[patent rights]] to CRISPR were contested. Several companies formed to develop related drugs and research tools.<ref name="TR">{{cite web | url = http://www.technologyreview.com/featuredstory/532796/who-owns-the-biggest-biotech-discovery-of-the-century/ | title = Who Owns the Biggest Biotech Discovery of the Century? There's a bitter fight over the patents for CRISPR, a breakthrough new form of DNA editing. | quote = CRISPR Patents Spark Fight to Control Genome Editing | work = MIT [[Technology Review]] | accessdate = 25 February 2015 }}</ref> As companies ramp up financing, doubts as to whether CRISPR can be quickly monetized were raised.<ref>{{cite web | last1 = Fye | first1 = Shaan | name-list-format = vanc | title=Genetic Rough Draft: Editas and CRISPR | url = http://atlasbusinessjournal.org/genetics/ | website = The Atlas Business Journal | accessdate = 19 January 2016 }}</ref> In February 2017 the US Patent Office ruled on a [[patent interference]] case brought by University of California with respect to patents issued to the [[Broad Institute]], and found that the Broad patents, with claims covering the application of CRISPR/cas9 in eukaryotic cells, were distinct from the inventions claimed by University of California.<ref>{{cite news | last1 = Pollack | first1 = Andrew | name-list-format = vanc | title = Harvard and M.I.T. Scientists Win Gene-Editing Patent Fight | url = https://www.nytimes.com/2017/02/15/science/broad-institute-harvard-mit-gene-editing-patent.html | work = The New York Times | date = 15 February 2017 }}</ref><ref>{{cite news | last1 = Akst | first1=Jef | name-list-format = vanc |title=Broad Wins CRISPR Patent Interference Case | url = http://www.the-scientist.com/?articles.view/articleNo/48490/title/Broad-Wins-CRISPR-Patent-Interference-Case | work = The Scientist Magazine | date=February 15, 2017 }}</ref><ref>{{cite news | last1 = Noonan | first1 = Kevin E.| name-list-format = vanc | title = PTAB Decides CRISPR Interference in Favor of Broad Institute -- Their Reasoning | url = http://www.patentdocs.org/2017/02/ptab-decides-crispr-interference-in-favor-of-broad-institute-their-reasoning.html | work = Patent Docs | date = February 16, 2017 }}</ref> |
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Shortly after, University of California filed an appeal of this ruling.<ref name="Potenza">{{cite news | last1 = Potenza | first1 = Alessandra | name-list-format = vanc | title = UC Berkeley challenges decision that CRISPR patents belong to Broad Institute 3 comments The legal fight will likely continue for months or even years | url = https://www.theverge.com/2017/4/13/15278478/crispr-gene-editing-tool-patent-dispute-appeal-ucb-mit-broad | accessdate=22 September 2017 | work=The Verge|date=April 13, 2017}}</ref><ref name="Buhr">{{cite news|last1=Buhr|first1=Sarah| name-list-format = vanc |title=The CRISPR patent battle is back on as UC Berkeley files an appeal|url=https://techcrunch.com/2017/07/26/the-crispr-patent-battle-is-back-on-as-uc-berkeley-files-an-appeal/|accessdate=22 September 2017|work=TechCrunch|date=July 26, 2017}}</ref> |
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As of November 2013, SAGE Labs (part of [[Horizon Discovery]] group) had [[exclusive right]]s from one of those companies to produce and sell genetically engineered rats and non-exclusive rights for mouse and rabbit models.<ref>{{cite web | url = http://www.genengnews.com/insight-and-intelligence/crispr-madness/77899947/ | title = CRISPR Madness | work = GEN }}</ref> {{As of|2015|alt=By 2015}}, [[Thermo Fisher Scientific]] had licensed intellectual property from ToolGen to develop CRISPR reagent kits.<ref>{{Cite journal|last=Staff|date=1 April 2015|title=News: Products & Services|journal=[[Gen. Eng. Biotechnol. News|Genetic Engineering & Biotechnology News]]|type=Paper|volume=35|issue=7|page=8}}</ref> |
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In March 2017, the European Patent Office (EPO) announced its intention to allow claims to Max-Planck Institute in Berlin, University of California, and University of Vienna,<ref name="Philippidis"/><ref name="Akst">{{cite news|last1=Akst|first1=Jef| name-list-format = vanc |title=UC Berkeley Receives CRISPR Patent in Europe|url=http://www.the-scientist.com/?articles.view/articleNo/48987/title/UC-Berkeley-Receives-CRISPR-Patent-in-Europe/|accessdate=22 September 2017|work=The Scientist|date=March 24, 2017}}</ref> and in August 2017, the EPO announced its intention to allow CRISPR claims in a patent application that MilliporeSigma had filed.<ref name="Philippidis">{{cite news|last1=Philippidis|first1=Alex|title=MilliporeSigma to Be Granted European Patent for CRISPR Technology|work=Genetic Engineering & Biotechology News|date=August 7, 2017|url=http://www.genengnews.com/gen-news-highlights/milliporesigma-to-be-granted-european-patent-for-crispr-technology/81254776|accessdate=22 September 2017}}</ref> As of August 2017 the patent situation in Europe was complex, with MilliporeSigma, ToolGen, Vilnius University, and Harvard contending for claims, along with University of California and Broad.<ref>{{cite journal | last1 = Cohen | first1 = Jon | name-list-format = vanc | title = CRISPR patent battle in Europe takes a ‘wild’ twist with surprising player|journal=Science|date=4 August 2017 | doi = 10.1126/science.aan7211 | url = http://www.sciencemag.org/news/2017/08/crispr-patent-battle-europe-takes-wild-twist-surprising-player }}</ref> |
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== Society and culture == |
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=== Human germline modification === |
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On Jan 21, 2018, The Wall Street Journal reported that 86 people in China have had their genes edited using CRISPR.<ref name = "WSJ_2018">{{cite news | url = https://www.wsj.com/articles/china-unhampered-by-rules-races-ahead-in-gene-editing-trials-1516562360 | title = China, Unhampered by Rules, Races Ahead in Gene-Editing Trials | last1 = Rana | first1 = Preetika | last2 = Marcus | first2 = Amy Dockser | last3 = Fan | first3 = Wenxin | name-list-format = vanc | date = 2018-01-21 | work = Wall Street Journal | access-date = 2018-01-23 | issn = 0099-9660 }}</ref><ref>{{cite news | url = https://gizmodo.com/china-has-already-gene-edited-86-people-with-crispr-1822297524 | title = China Has Already Gene-Edited 86 People With CRISPR | last = Brown | first = Kristen V. | name-list-format = vanc | work = Gizmodo | access-date = 2018-01-23 }}</ref> |
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At least four labs in the US, labs in China and the UK, and a US biotechnology company called Ovascience announced plans for ongoing research to apply CRISPR to human embryos.<ref>{{cite journal | first = Antonio | last = Regalado | name-list-format = vanc | journal = MIT Technology Review | date = March 5, 2015 | url = http://www.technologyreview.com/featuredstory/535661/engineering-the-perfect-baby/ | title = Engineering the Perfect Baby }}</ref> Scientists, including a CRISPR co-inventor, urged a worldwide moratorium on applying CRISPR to the human germline, especially for clinical use. They said "scientists should avoid even attempting, in lax jurisdictions, germline genome modification for clinical application in humans" until the full implications "are discussed among scientific and governmental organizations".<ref name="SCI-20150319">{{cite journal | vauthors = Baltimore D, Berg P, Botchan M, Carroll D, Charo RA, Church G, Corn JE, Daley GQ, Doudna JA, Fenner M, Greely HT, Jinek M, Martin GS, Penhoet E, Puck J, Sternberg SH, Weissman JS, Yamamoto KR | title = Biotechnology. A prudent path forward for genomic engineering and germline gene modification | journal = Science | volume = 348 | issue = 6230 | pages = 36–8 | date = April 2015 | pmid = 25791083 | pmc = 4394183 | doi = 10.1126/science.aab1028 | bibcode = 2015Sci...348...36B }}</ref><ref name="NAT-20150312">{{cite journal | vauthors = Lanphier E, Urnov F, Haecker SE, Werner M, Smolenski J | title = Don't edit the human germ line | journal = Nature | volume = 519 | issue = 7544 | pages = 410–1 | date = March 2015 | pmid = 25810189 | doi = 10.1038/519410a | bibcode = 2015Natur.519..410L }}</ref> These scientists support basic research on CRISPR and do not see CRISPR as developed enough for any clinical use in making heritable changes to humans.<ref name="NYT-20150319">{{cite news | last = Wade | first = Nicholas | name-list-format = vanc | title = Scientists Seek Ban on Method of Editing the Human Genome | url = https://www.nytimes.com/2015/03/20/science/biologists-call-for-halt-to-gene-editing-technique-in-humans.html | date =19 March 2015 | work = [[The New York Times]] | accessdate = 20 March 2015 | quote = The biologists writing in Science support continuing laboratory research with the technique, and few if any scientists believe it is ready for clinical use.}}</ref> |
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In April 2015, Chinese scientists reported results of an attempt to alter the [[DNA]] of non-viable [[human embryos]] using CRISPR to correct a [[mutation]] that causes [[beta thalassemia]], a lethal heritable disorder.<ref name="LiangXu2015">{{cite journal | vauthors = Liang P, Xu Y, Zhang X, Ding C, Huang R, Zhang Z, Lv J, Xie X, Chen Y, Li Y, Sun Y, Bai Y, Songyang Z, Ma W, Zhou C, Huang J | title = CRISPR/Cas9-mediated gene editing in human tripronuclear zygotes | journal = Protein & Cell | volume = 6 | issue = 5 | pages = 363–72 | date = May 2015 | pmid = 25894090 | pmc = 4417674 | doi = 10.1007/s13238-015-0153-5 }}</ref><ref name="NYT-20150423">{{cite news | last = Kolata | first = Gina | name-list-format = vanc | title=Chinese Scientists Edit Genes of Human Embryos, Raising Concerns |url=https://www.nytimes.com/2015/04/24/health/chinese-scientists-edit-genes-of-human-embryos-raising-concerns.html |date=23 April 2015 |work=[[The New York Times]] |accessdate=24 April 2015 }}</ref> The study had previously been rejected by both ''[[Nature (journal)|Nature]]'' and ''[[Science (journal)|Science]]'' in part because of ethical concerns.<ref name=NatureNews>{{cite journal |doi=10.1038/nature.2015.17378 |title=Chinese scientists genetically modify human embryos |journal=Nature |year=2015 |last1=Cyranoski |first1=David |last2=Reardon |first2=Sara | name-list-format = vanc }}</ref> The experiments resulted in changing only some genes, and had [[Off-target effects of genome editing|off-target effects]] on other genes. The researchers stated that CRISPR is not ready for clinical application in [[reproductive medicine]].<ref name=NatureNews/> In April 2016 Chinese scientists were reported to have made a second unsuccessful attempt to alter the DNA of non-viable human embryos using CRISPR - this time to alter the [[CCR5]] gene to make the embryo HIV resistant.<ref>{{Cite web|url=https://www.technologyreview.com/s/601235/chinese-researchers-experiment-with-making-hiv-proof-embryos/|title=Chinese Researchers Experiment with Making HIV-Proof Embryos|last=Regalado|first=Antonio|name-list-format = vanc |date=2016-05-08|website=MIT Technology Review|access-date=2016-06-10}}</ref> |
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In December 2015, an International Summit on Human Gene Editing took place in Washington under the guidance of [[David Baltimore]]. Members of national scientific academies of America, Britain and China discussed the ethics of germline modification. They agreed to support basic and clinical research under appropriate legal and ethical guidelines. A specific distinction was made between [[somatic cells]], where the effects of edits are limited to a single individual, versus germline cells, where genome changes could be inherited by future generations. Heritable modifications could have unintended and far-reaching consequences for human evolution, genetically (e.g. gene/environment interactions) and culturally (e.g. [[Social Darwinism]]). Altering of [[gametocytes]] and embryos to generate inheritable changes in humans was defined to be irresponsible. The group agreed to initiate an international forum to address such concerns and harmonize regulations across countries.<ref name="National Academy of Science">{{cite web | url = http://www8.nationalacademies.org/onpinews/newsitem.aspx?RecordID=12032015a | date =3 December 2015 | title = International Summit on Gene Editing | publisher =[[National Academies of Sciences, Engineering, and Medicine]] | accessdate = 3 December 2015 }}</ref> |
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=== Policy barriers to genetic engineering === |
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Policy regulations for the CRISPR/cas9 system vary around the globe. In February 2016, British scientists were given permission by regulators to genetically modify [[human embryos]] by using CRISPR-Cas9 and related techniques. However, researchers were forbidden from implanting the embryos and the embryos were to be destroyed after seven days.<ref>{{cite journal | vauthors = Callaway E | title = UK scientists gain licence to edit genes in human embryos | journal = Nature | volume = 530 | issue = 7588 | pages = 18 | date = February 2016 | pmid = 26842037 | doi = 10.1038/nature.2016.19270 | bibcode = 2016Natur.530...18C }}</ref> |
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The US has an elaborate, interdepartmental regulatory system to evaluate new genetically modified foods and crops. For example, the [[Agriculture Risk Protection Act of 2000]] gives the [[United States Department of Agriculture|USDA]] the authority to oversee the detection, control, eradication, suppression, prevention, or retardation of the spread of plant pests or noxious weeds to protect the agriculture, environment and economy of the US. The act regulates any [[genetically modified organism]] that utilizes the genome of a predefined 'plant pest' or any plant not previously categorized.<ref>{{cite journal | vauthors = McHughen A, Smyth S | title = US regulatory system for genetically modified [genetically modified organism (GMO), rDNA or transgenic] crop cultivars | journal = Plant Biotechnology Journal | volume = 6 | issue = 1 | pages = 2–12 | date = January 2008 | pmid = 17956539 | doi = 10.1111/j.1467-7652.2007.00300.x }}</ref> In 2015, Yinong Yang successfully deactivated 16 specific genes in the white button mushroom. Since he had not added any foreign DNA to his organism, the mushroom could not be regulated by the USDA under Section 340.2.<ref>{{cite web|url=https://www.aphis.usda.gov/biotechnology/downloads/reg_loi/15-321-01_air_response_signed.pdf|title=Re: Request to confirm <!-- too lazy to type -->|author=USDA|authorlink=USDA}}</ref> Yang's white button mushroom was the first organism genetically modified with the Crispr/cas9 protein system to pass US regulation.<ref name="Waltz_2016">{{cite journal | vauthors = Waltz E | title = Gene-edited CRISPR mushroom escapes US regulation | journal = Nature | volume = 532 | issue = 7599 | pages = 293 | year = 2016 | pmid = 27111611 | doi = 10.1038/nature.2016.19754 | bibcode = 2016Natur.532..293W }}</ref> In 2016, the USDA sponsored a committee to consider future regulatory policy for upcoming genetic modification techniques. With the help of the US [[National Academies of Sciences, Engineering, and Medicine|National Academies of Sciences, Engineering and Medicine]], special interests groups met on April 15 to contemplate the possible advancements in genetic engineering within the next 5 years and potential policy regulations that would need to come into play.<ref>{{cite journal | vauthors = Ledford H | title = Gene-editing surges as US rethinks regulations | journal = Nature | volume = 532 | issue = 7598 | pages = 158–9 | date = April 2016 | pmid = 27075074 | doi = 10.1038/532158a | bibcode = 2016Natur.532..158L }}</ref> With the emergence of rogue genetic engineers employing the technology, the [[FDA]] has begun issuing new regulations.<ref>[http://www.gizmodo.com.au/2017/02/the-fda-is-cracking-down-on-rogue-genetic-engineers/ "The FDA Is Cracking Down On Rogue Genetic Engineers"], Kristen V. Brown. Gizmodo. February 1, 2017. Retrieved 5 feb 2017</ref> |
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In China, where social conditions sharply contrast with the west, genetic diseases carry a heavy stigma, individuals with mental and physical disabilities get little government support. Furthermore, there are no religious barriers for the use of genetic modifications to change the genotypes of people.<ref name="Cyranoski_2017">{{cite journal | vauthors = Cyranoski D | title = China's embrace of embryo selection raises thorny questions | journal = Nature | volume = 548 | issue = 7667 | pages = 272–274 | year = 2017 | pmid = 28816265 | doi = 10.1038/548272a }}</ref> This leaves China with fewer policy barriers to the use of this technology.<ref name="Peng_2016">{{cite journal | vauthors = Peng Y | title = The morality and ethics governing CRISPR-Cas9 patents in China | journal = Nature Biotechnology | volume = 34 | issue = 6 | pages = 616–8 | year = 2016 | pmid = 27281418 | doi = 10.1038/nbt.3590 }}</ref><ref name = "WSJ_2018" /> |
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=== Recognition === |
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[[File:Professor Jennifer Doudna ForMemRS.jpg|thumb|Jennifer Doudna]] |
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In 2012 and 2013, CRISPR was a runner-up in ''[[Science Magazine]]''<nowiki/>'s [[Breakthrough of the Year]] award. In 2015, it was the winner of that award.<ref name="Science_Breakthrough"/> CRISPR was named as one of ''[[MIT Technology Review]]''{{'}}s 10 breakthrough technologies in 2014 and 2016.<ref name="MITCRISPR">{{cite news | last1 = Talbot | first1 = David | name-list-format = vanc | title = Precise Gene Editing in Plants/ 10 Breakthrough Technologies 2016 |url=https://www.technologyreview.com/s/600765/10-breakthrough-technologies-2016-precise-gene-editing-in-plants/ |accessdate=18 March 2016 | work = MIT Technology review | publisher = Massachusetts Institute of Technology|date=2016}}</ref><ref name="MITGene">{{cite news | last1 = Larson | first1 = Christina | last2 = Schaffer | first2 = Amanda | name-list-format = vanc | title=Genome Editing/ 10 Breakthrough Technologies 2014 | url =https://www.technologyreview.com/s/526511/genome-editing/ | accessdate=18 March 2016 | publisher =Massachusetts Institute of Technology | date = 2014 }}</ref> In 2016, [[Jennifer Doudna]], [[Emmanuelle Charpentier]], along with Rudolph Barrangou, [[Philippe Horvath]], and [[Feng Zhang]] won the Gairdner International award. In 2017, [[Jennifer Doudna]] and Emmanuelle Charpentier were awarded the Japan Prize for their revolutionary invention of CRISPR-Cas9 in Tokyo, Japan. |
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=== Alternative cutters === |
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<gallery class="center" title="Gallery of secondary structure images"> |
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Image:RF01315.png|'''CRISPR-DR2''': Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF01315 RF01315]. |
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Image:RF00003.jpg|'''CRISPR-DR3''': Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF00003 U1 snRNA]. |
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Image:RF01318.png|'''CRISPR-DR5''': Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF01318 RF011318]. |
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Image:RF01319.png|'''CRISPR-DR6''': Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF01319 RF01319]. |
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Image:RF01321.png|'''CRISPR-DR8''': Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF01321 RF01321]. |
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Image:RF01322.png|'''CRISPR-DR9''': Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF01322 RF01322]. |
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Image:RF01332.png|'''CRISPR-DR19''': Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF01332 RF01332]. |
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Image:RF01350.png|'''CRISPR-DR41''': Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF01350 RF01350]. |
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Image:RF01365.png|'''CRISPR-DR52''': Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF01365 RF01365]. |
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Image:RF01370.png|'''CRISPR-DR57''': Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF01370 RF01370]. |
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Image:RF01378.png|'''CRISPR-DR65''': Secondary structure taken from the [http://rfam.xfam.org Rfam] database. Family [http://rfam.xfam.org/family/RF01378 RF01378]. |
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</gallery> |
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== See also == |
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{{div col|2}} |
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* [[CRISPR/Cas Tools]] |
* [[CRISPR/Cas Tools]] |
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* [[CRISPR gene editing]] |
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* [[The CRISPR Journal]] |
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* "[[Designer baby]]" |
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* [[DRACO]] |
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* [[Gene knockout]] |
* [[Gene knockout]] |
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* [[Genome-wide CRISPR-Cas9 knockout screens]] |
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* [[Glossary of genetics]] |
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* [[Human germline engineering]] |
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* [[Human Nature (2019 film)|''Human Nature'' (2019 documentary film)]] |
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* [[MAGESTIC]] |
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* [[New eugenics|''New'' eugenics]] |
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* [[Prime editing]] |
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* [[RNAi]] |
* [[RNAi]] |
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* [[SiRNA]] |
* [[SiRNA]] |
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* [[Surveyor nuclease assay]] |
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* [[Synthetic biology]] |
* [[Synthetic biology]] |
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* [[ |
* [[Zinc finger]] |
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* [[DRACO]] |
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{{div col end}} |
{{div col end}} |
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== |
==Notes== |
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{{ |
{{Reflist|group=Note}} |
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{{clear}} |
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== References == |
== References == |
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{{ |
{{reflist}} |
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== Further reading == |
== Further reading == |
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{{Refbegin|30em}} |
{{Refbegin|30em}} |
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* {{cite book | |
* {{cite book | vauthors = Doudna J, Mali P | author-link1 = Jennifer Doudna | title = CRISPR-Cas: A Laboratory Manual | date = 23 March 2016 | publisher = Cold Spring Harbor Laboratory Press | location = New York | isbn = 978-1-62182-131-1 }} |
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* {{cite journal | vauthors = Mohanraju P, Makarova KS, Zetsche B, Zhang F, Koonin EV, van der Oost J | title = Diverse evolutionary roots and mechanistic variations of the CRISPR-Cas systems | journal = Science | volume = 353 | issue = 6299 | pages = aad5147 | date = August 2016 | pmid = |
* {{cite journal | vauthors = Mohanraju P, Makarova KS, Zetsche B, Zhang F, Koonin EV, van der Oost J | author-link4 = Feng Zhang | author-link5 = Eugene Koonin | title = Diverse evolutionary roots and mechanistic variations of the CRISPR-Cas systems | journal = Science | volume = 353 | issue = 6299 | pages = aad5147 | date = August 2016 | pmid = 27493190 | doi = 10.1126/science.aad5147 | hdl = 1721.1/113195 | hdl-access = free }} |
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* {{cite journal | vauthors = Sander JD, Joung JK | title = CRISPR-Cas systems for editing, regulating and targeting genomes | journal = Nature Biotechnology | volume = 32 | issue = 4 | pages = |
* {{cite journal | vauthors = Sander JD, Joung JK | title = CRISPR-Cas systems for editing, regulating and targeting genomes | journal = Nature Biotechnology | volume = 32 | issue = 4 | pages = 347–355 | date = April 2014 | pmid = 24584096 | pmc = 4022601 | doi = 10.1038/nbt.2842 }} |
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* {{cite journal | vauthors = Slaymaker IM, Gao L, Zetsche B, Scott DA, Yan WX, Zhang F | title = Rationally engineered Cas9 nucleases with improved specificity | journal = Science | volume = 351 | issue = 6268 | pages = |
* {{cite journal | vauthors = Slaymaker IM, Gao L, Zetsche B, Scott DA, Yan WX, Zhang F | author-link6=Feng Zhang | title = Rationally engineered Cas9 nucleases with improved specificity | journal = Science | volume = 351 | issue = 6268 | pages = 84–88 | date = January 2016 | pmid = 26628643| doi = 10.1126/science.aad5227 | pmc=4714946| bibcode = 2016Sci...351...84S }} |
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* {{cite journal | vauthors = Terns RM, Terns MP | title = CRISPR-based technologies: prokaryotic defense weapons repurposed | journal = Trends in Genetics | volume = 30 | issue = 3 | pages = |
* {{cite journal | vauthors = Terns RM, Terns MP | title = CRISPR-based technologies: prokaryotic defense weapons repurposed | journal = Trends in Genetics | volume = 30 | issue = 3 | pages = 111–118 | date = March 2014 | pmid = 24555991 | pmc = 3981743 | doi = 10.1016/j.tig.2014.01.003 }} |
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* {{cite journal | vauthors = Westra ER, Buckling A, Fineran PC | title = CRISPR-Cas systems: beyond adaptive immunity | journal = Nature Reviews Microbiology | volume = 12 | issue = 5 | pages = |
* {{cite journal | vauthors = Westra ER, Buckling A, Fineran PC | title = CRISPR-Cas systems: beyond adaptive immunity | journal = Nature Reviews Microbiology | volume = 12 | issue = 5 | pages = 317–326 | date = May 2014 | pmid = 24704746 | doi = 10.1038/nrmicro3241 }} |
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* {{cite journal | vauthors = Andersson AF, Banfield JF | title = Virus population dynamics and acquired virus resistance in natural microbial communities | journal = Science | volume = 320 | issue = 5879 | pages = |
* {{cite journal | vauthors = Andersson AF, Banfield JF | title = Virus population dynamics and acquired virus resistance in natural microbial communities | journal = Science | volume = 320 | issue = 5879 | pages = 1047–1050 | date = May 2008 | pmid = 18497291 | doi = 10.1126/science.1157358 | bibcode = 2008Sci...320.1047A }} |
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* {{cite journal | vauthors = Hale C, Kleppe K, Terns RM, Terns MP | title = Prokaryotic silencing (psi)RNAs in Pyrococcus furiosus | journal = RNA | volume = 14 | issue = 12 | pages = |
* {{cite journal | vauthors = Hale C, Kleppe K, Terns RM, Terns MP | title = Prokaryotic silencing (psi)RNAs in Pyrococcus furiosus | journal = RNA | volume = 14 | issue = 12 | pages = 2572–2579 | date = December 2008 | pmid = 18971321 | pmc = 2590957 | doi = 10.1261/rna.1246808 }} |
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* {{cite journal | vauthors = van der Ploeg JR | title = Analysis of CRISPR in Streptococcus mutans suggests frequent occurrence of acquired immunity against infection by M102-like bacteriophages | journal = Microbiology | volume = 155 | issue = Pt 6 | pages = |
* {{cite journal | vauthors = van der Ploeg JR | title = Analysis of CRISPR in Streptococcus mutans suggests frequent occurrence of acquired immunity against infection by M102-like bacteriophages | journal = Microbiology | volume = 155 | issue = Pt 6 | pages = 1966–1976 | date = June 2009 | pmid = 19383692 | doi = 10.1099/mic.0.027508-0 | doi-access = free }} |
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* {{cite journal | vauthors = van der Oost J, Brouns SJ | title = RNAi: prokaryotes get in on the act | journal = Cell | volume = 139 | issue = 5 | pages = |
* {{cite journal | vauthors = van der Oost J, Brouns SJ | title = RNAi: prokaryotes get in on the act | journal = Cell | volume = 139 | issue = 5 | pages = 863–865 | date = November 2009 | pmid = 19945373 | doi = 10.1016/j.cell.2009.11.018 | doi-access = free }} |
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* {{cite journal | vauthors = Karginov FV, Hannon GJ | title = The CRISPR system: small RNA-guided defense in bacteria and archaea | journal = Molecular Cell | volume = 37 | issue = 1 | pages = 7–19 | date = January 2010 | pmid = 20129051 | pmc = 2819186 | doi = 10.1016/j.molcel.2009.12.033 }} |
* {{cite journal | vauthors = Karginov FV, Hannon GJ | title = The CRISPR system: small RNA-guided defense in bacteria and archaea | journal = Molecular Cell | volume = 37 | issue = 1 | pages = 7–19 | date = January 2010 | pmid = 20129051 | pmc = 2819186 | doi = 10.1016/j.molcel.2009.12.033 }} |
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* {{cite journal | vauthors = Pul U, Wurm R, Arslan Z, Geissen R, Hofmann N, Wagner R | title = Identification and characterization of E. coli CRISPR-cas promoters and their silencing by H-NS | journal = Molecular Microbiology | volume = 75 | issue = 6 | pages = |
* {{cite journal | vauthors = Pul U, Wurm R, Arslan Z, Geissen R, Hofmann N, Wagner R | title = Identification and characterization of E. coli CRISPR-cas promoters and their silencing by H-NS | journal = Molecular Microbiology | volume = 75 | issue = 6 | pages = 1495–1512 | date = March 2010 | pmid = 20132443 | doi = 10.1111/j.1365-2958.2010.07073.x | doi-access = free }} |
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* {{cite journal | vauthors = Díez-Villaseñor C, Almendros C, García-Martínez J, Mojica FJ | title = Diversity of CRISPR loci in Escherichia coli | journal = Microbiology | volume = 156 | issue = Pt 5 | pages = |
* {{cite journal | vauthors = Díez-Villaseñor C, Almendros C, García-Martínez J, Mojica FJ | title = Diversity of CRISPR loci in ''Escherichia coli'' | journal = Microbiology | volume = 156 | issue = Pt 5 | pages = 1351–1361 | date = May 2010 | pmid = 20133361 | doi = 10.1099/mic.0.036046-0 | doi-access = free }} |
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* {{cite journal | vauthors = Deveau H, Garneau JE, Moineau S | title = CRISPR/Cas system and its role in phage-bacteria interactions | journal = Annual Review of Microbiology | volume = 64 | pages = |
* {{cite journal | vauthors = Deveau H, Garneau JE, Moineau S | title = CRISPR/Cas system and its role in phage-bacteria interactions | journal = Annual Review of Microbiology | volume = 64 | pages = 475–493 | year = 2010 | pmid = 20528693 | doi = 10.1146/annurev.micro.112408.134123 }} |
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* {{cite journal | vauthors = Koonin EV, Makarova KS | title = CRISPR-Cas: an adaptive immunity system in prokaryotes | journal = F1000 Biology Reports | volume = 1 | |
* {{cite journal | vauthors = Koonin EV, Makarova KS | author-link=Eugene Koonin | title = CRISPR-Cas: an adaptive immunity system in prokaryotes | journal = F1000 Biology Reports | volume = 1 | page = 95 | date = December 2009 | pmid = 20556198 | pmc = 2884157 | doi = 10.3410/B1-95 | doi-access=free }} |
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* {{Cite news|title = The age of the red pen|url = https://www.economist.com/news/briefing/21661799-it-now-easy-edit-genomes-plants-animals-and-humans-age-red-pen|newspaper = The Economist|access-date = 2015-08-25|issn = 0013-0613|date = August 22, 2015}} |
* {{Cite news|title = The age of the red pen|url = https://www.economist.com/news/briefing/21661799-it-now-easy-edit-genomes-plants-animals-and-humans-age-red-pen|newspaper = The Economist|access-date = 2015-08-25|issn = 0013-0613|date = August 22, 2015|archive-date = 2015-08-24|archive-url = https://web.archive.org/web/20150824054220/http://www.economist.com/news/briefing/21661799-it-now-easy-edit-genomes-plants-animals-and-humans-age-red-pen|url-status = live}} |
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* {{cite journal | vauthors = Ran AF, Hsu PD, Wright J, Agarwala V, Scott DA, Zhang F | title = Genome engineering using the CRISPR-Cas9 system. | journal = Nature Protocols | volume = 8 | issue = 11 | pages = 2281–2308 | date = 2013 | pmid = 24157548 | pmc = 3969860 | doi = 10.1038/nprot.2013.143 }} |
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{{refend}} |
{{refend}} |
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== External links == |
== External links == |
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{{Commons category}} |
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* [https://fas.org/sgp/crs/misc/R44824.pdf Advanced Gene Editing: CRISPR-Cas9] [[Congressional Research Service]] |
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{{Scholia|topic}} |
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* [https://www.ibiology.org/ibiomagazine/jennifer-doudna-genome-engineering-with-crispr-cas9-birth-of-a-breakthrough-technology.html Jennifer Doudna talk: Genome Engineering with CRISPR-Cas9: Birth of a Breakthrough Technology] |
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* {{cite web|url=https://fas.org/sgp/crs/misc/R44824.pdf |title=Advanced Gene Editing: CRISPR-Cas9 |publisher=[[Congressional Research Service]]}} |
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{{Breakthrough of the Year}} |
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* {{cite web|url=https://www.ibiology.org/ibiomagazine/jennifer-doudna-genome-engineering-with-crispr-cas9-birth-of-a-breakthrough-technology.html |title=Jennifer Doudna talk: Genome Engineering with CRISPR-Cas9: Birth of a Breakthrough Technology|date=10 September 2022 }} |
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*{{cite episode|title=Human Nature|series=NOVA|series-link=Nova (American TV program)|network=[[PBS]]|station=[[WGBH-TV|WGBH]]|date=September 9, 2020|season=47|number=9|url=https://www.pbs.org/wgbh/nova/video/human-nature/|access-date=April 7, 2023}} |
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===Protein Data Bank=== |
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* {{PDBe-KB2|Q46901|CRISPR system Cascade subunit CasA}} |
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* {{PDBe-KB2|P76632|CRISPR system Cascade subunit CasB}} |
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* {{PDBe-KB2|Q46899|CRISPR system Cascade subunit CasC}} |
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* {{PDBe-KB2|Q46898|CRISPR system Cascade subunit CasD}} |
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* {{PDBe-KB2|Q46897|CRISPR system Cascade subunit CasE}} |
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{{Glossaries of science and engineering}} |
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{{Repeated sequence}} |
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Latest revision as of 14:25, 13 December 2024
Cascade (CRISPR-associated complex for antiviral defense) | |||||||
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Identifiers | |||||||
Organism | |||||||
Symbol | CRISPR | ||||||
Entrez | 947229 | ||||||
PDB | 4QYZ | ||||||
RefSeq (Prot) | NP_417241.1 | ||||||
UniProt | P38036 | ||||||
|
Part of a series on |
CRISPR |
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Genome editing: CRISPR-Cas |
variants: Anti-CRISPR - CIRTS - CRISPeYCRISPR-Cas10 - CRISPR-Cas13 - CRISPR-BEST CRISPR-Disp - CRISPR-Gold - CRISPRa - CRISPRi Easi-CRISPR - FACE |
Enzyme |
Cas9 - FokI - EcoRI - PstI - SmaI HaeIII - Cas12a (Cpf1) - xCas9 |
Applications |
CAMERA - ICE - Genética dirigida |
other Genome editing method: |
Prime editing - Pro-AG - RESCUE - TALEN - ZFN - LEAPER |
Part of a series on |
Genetic engineering |
---|
Genetically modified organisms |
History and regulation |
Process |
Applications |
Controversies |
CRISPR (/ˈkrɪspər/) (an acronym for clustered regularly interspaced short palindromic repeats) is a family of DNA sequences found in the genomes of prokaryotic organisms such as bacteria and archaea.[2] Each sequence within an individual prokaryotic cell is derived from a DNA fragment of a bacteriophage that had previously infected the prokaryote or one of its ancestors.[3][4] These sequences are used to detect and destroy DNA from similar bacteriophages during subsequent infections. Hence these sequences play a key role in the antiviral (i.e. anti-phage) defense system of prokaryotes and provide a form of heritable,[3] acquired immunity.[2][5][6][7] CRISPR is found in approximately 50% of sequenced bacterial genomes and nearly 90% of sequenced archaea.[3]
Cas9 (or "CRISPR-associated protein 9") is an enzyme that uses CRISPR sequences as a guide to recognize and open up specific strands of DNA that are complementary to the CRISPR sequence. Cas9 enzymes together with CRISPR sequences form the basis of a technology known as CRISPR-Cas9 that can be used to edit genes within living organisms.[9][10] This editing process has a wide variety of applications including basic biological research, development of biotechnological products, and treatment of diseases.[11][12] The development of the CRISPR-Cas9 genome editing technique was recognized by the Nobel Prize in Chemistry in 2020 awarded to Emmanuelle Charpentier and Jennifer Doudna.[13][14]
History
[edit]Repeated sequences
[edit]The discovery of clustered DNA repeats took place independently in three parts of the world. The first description of what would later be called CRISPR is from Osaka University researcher Yoshizumi Ishino and his colleagues in 1987. They accidentally cloned part of a CRISPR sequence together with the "iap" gene (isozyme conversion of alkaline phosphatase) from their target genome, that of Escherichia coli.[15][16] The organization of the repeats was unusual. Repeated sequences are typically arranged consecutively, without interspersing different sequences.[12][16] They did not know the function of the interrupted clustered repeats.
In 1993, researchers of Mycobacterium tuberculosis in the Netherlands published two articles about a cluster of interrupted direct repeats (DR) in that bacterium. They recognized the diversity of the sequences that intervened in the direct repeats among different strains of M. tuberculosis[17] and used this property to design a typing method called spoligotyping, still in use today.[18][19]
Francisco Mojica at the University of Alicante in Spain studied the function of repeats in the archaeal species Haloferax and Haloarcula. Mojica's supervisor surmised that the clustered repeats had a role in correctly segregating replicated DNA into daughter cells during cell division, because plasmids and chromosomes with identical repeat arrays could not coexist in Haloferax volcanii. Transcription of the interrupted repeats was also noted for the first time; this was the first full characterization of CRISPR.[19][20] By 2000, Mojica and his students, after an automated search of published genomes, identified interrupted repeats in 20 species of microbes as belonging to the same family.[21] Because those sequences were interspaced, Mojica initially called these sequences "short regularly spaced repeats" (SRSR).[22] In 2001, Mojica and Ruud Jansen, who were searching for an additional interrupted repeats, proposed the acronym CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) to unify the numerous acronyms used to describe these sequences.[20][23] In 2002, Tang, et al. showed evidence that CRISPR repeat regions from the genome of Archaeoglobus fulgidus were transcribed into long RNA molecules subsequently processed into unit-length small RNAs, plus some longer forms of 2, 3, or more spacer-repeat units.[24][25]
In 2005, yogurt researcher Rodolphe Barrangou discovered that Streptococcus thermophilus, after iterative phage infection challenges, develops increased phage resistance due to the incorporation of additional CRISPR spacer sequences.[26] Barrangou's employer, the Danish food company Danisco, then developed phage-resistant S. thermophilus strains for yogurt production. Danisco was later bought by DuPont, which owns about 50 percent of the global dairy culture market, and the technology spread widely.[27]
CRISPR-associated systems
[edit]A major advance in understanding CRISPR came with Jansen's observation that the prokaryote repeat cluster was accompanied by four homologous genes that make up CRISPR-associated systems, cas 1–4. The Cas proteins showed helicase and nuclease motifs, suggesting a role in the dynamic structure of the CRISPR loci.[28] In this publication, the acronym CRISPR was used as the universal name of this pattern, but its function remained enigmatic.
In 2005, three independent research groups showed that some CRISPR spacers are derived from phage DNA and extrachromosomal DNA such as plasmids.[32][33][34] In effect, the spacers are fragments of DNA gathered from viruses that previously attacked the cell. The source of the spacers was a sign that the CRISPR-cas system could have a role in adaptive immunity in bacteria.[29][35] All three studies proposing this idea were initially rejected by high-profile journals, but eventually appeared in other journals.[36]
The first publication[33] proposing a role of CRISPR-Cas in microbial immunity, by Mojica and collaborators at the University of Alicante, predicted a role for the RNA transcript of spacers on target recognition in a mechanism that could be analogous to the RNA interference system used by eukaryotic cells. Koonin and colleagues extended this RNA interference hypothesis by proposing mechanisms of action for the different CRISPR-Cas subtypes according to the predicted function of their proteins.[37]
Experimental work by several groups revealed the basic mechanisms of CRISPR-Cas immunity. In 2007, the first experimental evidence that CRISPR was an adaptive immune system was published.[6][12] A CRISPR region in Streptococcus thermophilus acquired spacers from the DNA of an infecting bacteriophage. The researchers manipulated the resistance of S. thermophilus to different types of phages by adding and deleting spacers whose sequence matched those found in the tested phages.[38][39] In 2008, Brouns and Van der Oost identified a complex of Cas proteins called Cascade, that in E. coli cut the CRISPR RNA precursor within the repeats into mature spacer-containing RNA molecules called CRISPR RNA (crRNA), which remained bound to the protein complex.[40] Moreover, it was found that Cascade, crRNA and a helicase/nuclease (Cas3) were required to provide a bacterial host with immunity against infection by a DNA virus. By designing an anti-virus CRISPR, they demonstrated that two orientations of the crRNA (sense/antisense) provided immunity, indicating that the crRNA guides were targeting dsDNA. That year Marraffini and Sontheimer confirmed that a CRISPR sequence of S. epidermidis targeted DNA and not RNA to prevent conjugation. This finding was at odds with the proposed RNA-interference-like mechanism of CRISPR-Cas immunity, although a CRISPR-Cas system that targets foreign RNA was later found in Pyrococcus furiosus.[12][39] A 2010 study showed that CRISPR-Cas cuts strands of both phage and plasmid DNA in S. thermophilus.[41]
Cas9
[edit]A simpler CRISPR system from Streptococcus pyogenes relies on the protein Cas9. The Cas9 endonuclease is a four-component system that includes two small molecules: crRNA and trans-activating CRISPR RNA (tracrRNA).[42][43] In 2012, Jennifer Doudna and Emmanuelle Charpentier re-engineered the Cas9 endonuclease into a more manageable two-component system by fusing the two RNA molecules into a "single-guide RNA" that, when combined with Cas9, could find and cut the DNA target specified by the guide RNA.[44] This contribution was so significant that it was recognized by the Nobel Prize in Chemistry in 2020. By manipulating the nucleotide sequence of the guide RNA, the artificial Cas9 system could be programmed to target any DNA sequence for separation.[44] Another collaboration comprising Virginijus Šikšnys, Gasiūnas, Barrangou, and Horvath showed that Cas9 from the S. thermophilus CRISPR system can also be reprogrammed to target a site of their choosing by changing the sequence of its crRNA. These advances fueled efforts to edit genomes with the modified CRISPR-Cas9 system.[19]
Groups led by Feng Zhang and George Church simultaneously published descriptions of genome editing in human cell cultures using CRISPR-Cas9 for the first time.[12][45][46] It has since been used in a wide range of organisms, including baker's yeast (Saccharomyces cerevisiae),[47][48][49] the opportunistic pathogen Candida albicans,[50][51] zebrafish (Danio rerio),[52] fruit flies (Drosophila melanogaster),[53][54] ants (Harpegnathos saltator[55] and Ooceraea biroi[56]), mosquitoes (Aedes aegypti[57]), nematodes (Caenorhabditis elegans),[58] plants,[59] mice (Mus musculus domesticus),[60][61] monkeys[62] and human embryos.[63]
CRISPR has been modified to make programmable transcription factors that allows activation or silencing of targeted genes.[64]
The CRISPR-Cas9 system has been shown to make effective gene edits in Human tripronuclear zygotes, as first described in a 2015 paper by Chinese scientists P. Liang and Y. Xu. The system made a successful cleavage of mutant Beta-Hemoglobin (HBB) in 28 out of 54 embryos. Four out of the 28 embryos were successfully recombined using a donor template. The scientists showed that during DNA recombination of the cleaved strand, the homologous endogenous sequence HBD competes with the exogenous donor template. DNA repair in human embryos is much more complicated and particular than in derived stem cells.[65]
Cas12a
[edit]In 2015, the nuclease Cas12a (formerly called Cpf1[66]) was characterized in the CRISPR-Cpf1 system of the bacterium Francisella novicida.[67][68] Its original name, from a TIGRFAMs protein family definition built in 2012, reflects the prevalence of its CRISPR-Cas subtype in the Prevotella and Francisella lineages. Cas12a showed several key differences from Cas9 including: causing a 'staggered' cut in double stranded DNA as opposed to the 'blunt' cut produced by Cas9, relying on a 'T rich' PAM (providing alternative targeting sites to Cas9), and requiring only a CRISPR RNA (crRNA) for successful targeting. By contrast, Cas9 requires both crRNA and a trans-activating crRNA (tracrRNA).
These differences may give Cas12a some advantages over Cas9. For example, Cas12a's small crRNAs are ideal for multiplexed genome editing, as more of them can be packaged in one vector than can Cas9's sgRNAs. The sticky 5′ overhangs left by Cas12a can also be used for DNA assembly that is much more target-specific than traditional restriction enzyme cloning.[69] Finally, Cas12a cleaves DNA 18–23 base pairs downstream from the PAM site. This means there is no disruption to the recognition sequence after repair, and so Cas12a enables multiple rounds of DNA cleavage. By contrast, since Cas9 cuts only 3 base pairs upstream of the PAM site, the NHEJ pathway results in indel mutations that destroy the recognition sequence, thereby preventing further rounds of cutting. In theory, repeated rounds of DNA cleavage should cause an increased opportunity for the desired genomic editing to occur.[70] A distinctive feature of Cas12a, as compared to Cas9, is that after cutting its target, Cas12a remains bound to the target and then cleaves other ssDNA molecules non-discriminately.[71] This property is called "collateral cleavage" or "trans-cleavage" activity and has been exploited for the development of various diagnostic technologies.[72][73]
Cas13
[edit]In 2016, the nuclease Cas13a (formerly known as C2c2) from the bacterium Leptotrichia shahii was characterized. Cas13 is an RNA-guided RNA endonuclease, which means that it does not cleave DNA, but only single-stranded RNA. Cas13 is guided by its crRNA to a ssRNA target and binds and cleaves the target. Similar to Cas12a, the Cas13 remains bound to the target and then cleaves other ssRNA molecules non-discriminately.[74] This collateral cleavage property has been exploited for the development of various diagnostic technologies.[75][76][77]
In 2021, Dr. Hui Yang characterized novel miniature Cas13 protein (mCas13) variants, Cas13X and Cas13Y. Using a small portion of N gene sequence from SARS-CoV-2 as a target in characterization of mCas13, revealed the sensitivity and specificity of mCas13 coupled with RT-LAMP for detection of SARS-CoV-2 in both synthetic and clinical samples over other available standard tests like RT-qPCR (1 copy/μL).[78]
Locus structure
[edit]Repeats and spacers
[edit]The CRISPR array is made up of an AT-rich leader sequence followed by short repeats that are separated by unique spacers.[79] CRISPR repeats typically range in size from 28 to 37 base pairs (bps), though there can be as few as 23 bp and as many as 55 bp.[80] Some show dyad symmetry, implying the formation of a secondary structure such as a stem-loop ('hairpin') in the RNA, while others are designed to be unstructured. The size of spacers in different CRISPR arrays is typically 32 to 38 bp (range 21 to 72 bp).[80] New spacers can appear rapidly as part of the immune response to phage infection.[81] There are usually fewer than 50 units of the repeat-spacer sequence in a CRISPR array.[80]
CRISPR RNA structures
[edit]Cas genes and CRISPR subtypes
[edit]Small clusters of cas genes are often located next to CRISPR repeat-spacer arrays. Collectively the 93 cas genes are grouped into 35 families based on sequence similarity of the encoded proteins. 11 of the 35 families form the cas core, which includes the protein families Cas1 through Cas9. A complete CRISPR-Cas locus has at least one gene belonging to the cas core.[82]
CRISPR-Cas systems fall into two classes. Class 1 systems use a complex of multiple Cas proteins to degrade foreign nucleic acids. Class 2 systems use a single large Cas protein for the same purpose. Class 1 is divided into types I, III, and IV; class 2 is divided into types II, V, and VI.[83] The 6 system types are divided into 33 subtypes.[84] Each type and most subtypes are characterized by a "signature gene" found almost exclusively in the category. Classification is also based on the complement of cas genes that are present. Most CRISPR-Cas systems have a Cas1 protein. The phylogeny of Cas1 proteins generally agrees with the classification system,[85] but exceptions exist due to module shuffling.[82] Many organisms contain multiple CRISPR-Cas systems suggesting that they are compatible and may share components.[86][87] The sporadic distribution of the CRISPR-Cas subtypes suggests that the CRISPR-Cas system is subject to horizontal gene transfer during microbial evolution.
This table is missing information about UniProt and InterPro cross-reference.(October 2020) |
Class | Cas type | Cas subtype | Signature protein | Function | Reference |
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1 | I | — | Cas3 | Single-stranded DNA nuclease (HD domain) and ATP-dependent helicase | [88][89] |
I-A | Cas8a, Cas5 | Cas8 is a Subunit of the interference module that is important in targeting of invading DNA by recognizing the PAM sequence. Cas5 is required for processing and stability of crRNAs. | [85][90] | ||
I-B | Cas8b | ||||
I-C | Cas8c | ||||
I-D | Cas10d | contains a domain homologous to the palm domain of nucleic acid polymerases and nucleotide cyclases | [91][92] | ||
I-E | Cse1, Cse2 | ||||
I-F | Csy1, Csy2, Csy3 | Type IF-3 have been implicated in CRISPR-associated transposons | [85] | ||
I-G[Note 1] | GSU0054 | [93] | |||
III | — | Cas10 | Homolog of Cas10d and Cse1. Binds CRISPR target RNA and promotes stability of the interference complex | [92][94] | |
III-A | Csm2 | Not determined | [85] | ||
III-B | Cmr5 | Not determined | [85] | ||
III-C | Cas10 or Csx11 | [85][94] | |||
III-D | Csx10 | [85] | |||
III-E | [93] | ||||
III-F | [93] | ||||
IV | — | Csf1 | [93] | ||
IV-A | [93] | ||||
IV-B | [93] | ||||
IV-C | [93] | ||||
2 | II | — | Cas9 | Nucleases RuvC and HNH together produce DSBs, and separately can produce single-strand breaks. Ensures the acquisition of functional spacers during adaptation. | [95][96] |
II-A | Csn2 | Ring-shaped DNA-binding protein. Involved in primed adaptation in Type II CRISPR system. | [97] | ||
II-B | Cas4 | Endonuclease that works with cas1 and cas2 to generate spacer sequences | [98] | ||
II-C | Characterized by the absence of either Csn2 or Cas4 | [99] | |||
V | — | Cas12 | Nuclease RuvC. Lacks HNH. | [83][100] | |
V-A | Cas12a (Cpf1) | Auto-processing pre-crRNA activity for multiplex gene regulation | [93][101] | ||
V-B | Cas12b (C2c1) | [93] | |||
V-C | Cas12c (C2c3) | [93] | |||
V-D | Cas12d (CasY) | [93] | |||
V-E | Cas12e (CasX) | [93] | |||
V-F | Cas12f (Cas14, C2c10) | [93] | |||
V-G | Cas12g | [93] | |||
V-H | Cas12h | [93] | |||
V-I | Cas12i | [93] | |||
V-K[Note 2] | Cas12k (C2c5) | Type V-K have been implicated in CRISPR-associated transposons. | [93] | ||
V-U | C2c4, C2c8, C2c9 | [93] | |||
VI | — | Cas13 | RNA-guided RNase | [83][102] | |
VI-A | Cas13a (C2c2) | [93] | |||
VI-B | Cas13b | [93] | |||
VI-C | Cas13c | [93] | |||
VI-D | Cas13d | [93] | |||
VI-X | Cas13x.1 | RNA dependent RNA polymerase, Prophylactic RNA-virus inhibition | [103] | ||
VI-Y | [103] |
Mechanism
[edit]CRISPR-Cas immunity is a natural process of bacteria and archaea.[104] CRISPR-Cas prevents bacteriophage infection, conjugation and natural transformation by degrading foreign nucleic acids that enter the cell.[39]
Spacer acquisition
[edit]When a microbe is invaded by a bacteriophage, the first stage of the immune response is to capture phage DNA and insert it into a CRISPR locus in the form of a spacer. Cas1 and Cas2 are found in both types of CRISPR-Cas immune systems, which indicates that they are involved in spacer acquisition. Mutation studies confirmed this hypothesis, showing that removal of Cas1 or Cas2 stopped spacer acquisition, without affecting CRISPR immune response.[105][106][107][108][109]
Multiple Cas1 proteins have been characterised and their structures resolved.[110][111][112] Cas1 proteins have diverse amino acid sequences. However, their crystal structures are similar and all purified Cas1 proteins are metal-dependent nucleases/integrases that bind to DNA in a sequence-independent manner.[86] Representative Cas2 proteins have been characterised and possess either (single strand) ssRNA-[113] or (double strand) dsDNA-[114][115] specific endoribonuclease activity.
In the I-E system of E. coli Cas1 and Cas2 form a complex where a Cas2 dimer bridges two Cas1 dimers.[116] In this complex Cas2 performs a non-enzymatic scaffolding role,[116] binding double-stranded fragments of invading DNA, while Cas1 binds the single-stranded flanks of the DNA and catalyses their integration into CRISPR arrays.[117][118][119] New spacers are usually added at the beginning of the CRISPR next to the leader sequence creating a chronological record of viral infections.[120] In E. coli a histone like protein called integration host factor (IHF), which binds to the leader sequence, is responsible for the accuracy of this integration.[121] IHF also enhances integration efficiency in the type I-F system of Pectobacterium atrosepticum.[122] but in other systems, different host factors may be required[123]
Protospacer adjacent motifs (PAM)
[edit]Bioinformatic analysis of regions of phage genomes that were excised as spacers (termed protospacers) revealed that they were not randomly selected but instead were found adjacent to short (3–5 bp) DNA sequences termed protospacer adjacent motifs (PAM). Analysis of CRISPR-Cas systems showed PAMs to be important for type I and type II, but not type III systems during acquisition.[34][124][125][126][127][128] In type I and type II systems, protospacers are excised at positions adjacent to a PAM sequence, with the other end of the spacer cut using a ruler mechanism, thus maintaining the regularity of the spacer size in the CRISPR array.[129][130] The conservation of the PAM sequence differs between CRISPR-Cas systems and appears to be evolutionarily linked to Cas1 and the leader sequence.[128][131]
New spacers are added to a CRISPR array in a directional manner,[32] occurring preferentially,[81][124][125][132][133] but not exclusively, adjacent[127][130] to the leader sequence. Analysis of the type I-E system from E. coli demonstrated that the first direct repeat adjacent to the leader sequence is copied, with the newly acquired spacer inserted between the first and second direct repeats.[108][129]
The PAM sequence appears to be important during spacer insertion in type I-E systems. That sequence contains a strongly conserved final nucleotide (nt) adjacent to the first nt of the protospacer. This nt becomes the final base in the first direct repeat.[109][134][135] This suggests that the spacer acquisition machinery generates single-stranded overhangs in the second-to-last position of the direct repeat and in the PAM during spacer insertion. However, not all CRISPR-Cas systems appear to share this mechanism as PAMs in other organisms do not show the same level of conservation in the final position.[131] It is likely that in those systems, a blunt end is generated at the very end of the direct repeat and the protospacer during acquisition.
Insertion variants
[edit]Analysis of Sulfolobus solfataricus CRISPRs revealed further complexities to the canonical model of spacer insertion, as one of its six CRISPR loci inserted new spacers randomly throughout its CRISPR array, as opposed to inserting closest to the leader sequence.[130]
Multiple CRISPRs contain many spacers to the same phage. The mechanism that causes this phenomenon was discovered in the type I-E system of E. coli. A significant enhancement in spacer acquisition was detected where spacers already target the phage, even mismatches to the protospacer. This 'priming' requires the Cas proteins involved in both acquisition and interference to interact with each other. Newly acquired spacers that result from the priming mechanism are always found on the same strand as the priming spacer.[109][134][135] This observation led to the hypothesis that the acquisition machinery slides along the foreign DNA after priming to find a new protospacer.[135]
Biogenesis
[edit]CRISPR-RNA (crRNA), which later guides the Cas nuclease to the target during the interference step, must be generated from the CRISPR sequence. The crRNA is initially transcribed as part of a single long transcript encompassing much of the CRISPR array.[30] This transcript is then cleaved by Cas proteins to form crRNAs. The mechanism to produce crRNAs differs among CRISPR-Cas systems. In type I-E and type I-F systems, the proteins Cas6e and Cas6f respectively, recognise stem-loops[136][137][138] created by the pairing of identical repeats that flank the crRNA.[139] These Cas proteins cleave the longer transcript at the edge of the paired region, leaving a single crRNA along with a small remnant of the paired repeat region.
Type III systems also use Cas6, however, their repeats do not produce stem-loops. Cleavage instead occurs by the longer transcript wrapping around the Cas6 to allow cleavage just upstream of the repeat sequence.[140][141][142]
Type II systems lack the Cas6 gene and instead utilize RNaseIII for cleavage. Functional type II systems encode an extra small RNA that is complementary to the repeat sequence, known as a trans-activating crRNA (tracrRNA).[42] Transcription of the tracrRNA and the primary CRISPR transcript results in base pairing and the formation of dsRNA at the repeat sequence, which is subsequently targeted by RNaseIII to produce crRNAs. Unlike the other two systems, the crRNA does not contain the full spacer, which is instead truncated at one end.[95]
CrRNAs associate with Cas proteins to form ribonucleotide complexes that recognize foreign nucleic acids. CrRNAs show no preference between the coding and non-coding strands, which is indicative of an RNA-guided DNA-targeting system.[7][41][105][109][143][144][145] The type I-E complex (commonly referred to as Cascade) requires five Cas proteins bound to a single crRNA.[146][147]
Interference
[edit]During the interference stage in type I systems, the PAM sequence is recognized on the crRNA-complementary strand and is required along with crRNA annealing. In type I systems correct base pairing between the crRNA and the protospacer signals a conformational change in Cascade that recruits Cas3 for DNA degradation.
Type II systems rely on a single multifunctional protein, Cas9, for the interference step.[95] Cas9 requires both the crRNA and the tracrRNA to function and cleave DNA using its dual HNH and RuvC/RNaseH-like endonuclease domains. Basepairing between the PAM and the phage genome is required in type II systems. However, the PAM is recognized on the same strand as the crRNA (the opposite strand to type I systems).
Type III systems, like type I require six or seven Cas proteins binding to crRNAs.[148][149] The type III systems analysed from S. solfataricus and P. furiosus both target the mRNA of phages rather than phage DNA genome,[87][149] which may make these systems uniquely capable of targeting RNA-based phage genomes.[86] Type III systems were also found to target DNA in addition to RNA using a different Cas protein in the complex, Cas10.[150] The DNA cleavage was shown to be transcription dependent.[151]
The mechanism for distinguishing self from foreign DNA during interference is built into the crRNAs and is therefore likely common to all three systems. Throughout the distinctive maturation process of each major type, all crRNAs contain a spacer sequence and some portion of the repeat at one or both ends. It is the partial repeat sequence that prevents the CRISPR-Cas system from targeting the chromosome as base pairing beyond the spacer sequence signals self and prevents DNA cleavage.[152] RNA-guided CRISPR enzymes are classified as type V restriction enzymes.
Evolution
[edit]CRISPR associated protein Cas2 (adaptation RNase) | |||||||||
---|---|---|---|---|---|---|---|---|---|
Identifiers | |||||||||
Symbol | CRISPR_Cas2 | ||||||||
Pfam | PF09827 | ||||||||
InterPro | IPR019199 | ||||||||
CDD | cd09638 | ||||||||
|
CRISPR-associated protein CasA/Cse1 (Type I effector DNase) | |||||||||
---|---|---|---|---|---|---|---|---|---|
Identifiers | |||||||||
Symbol | CRISPR_Cse1 | ||||||||
Pfam | PF09481 | ||||||||
InterPro | IPR013381 | ||||||||
CDD | cd09729 | ||||||||
|
CRISPR associated protein CasC/Cse3/Cas6 (Type I effector RNase) | |||||||||
---|---|---|---|---|---|---|---|---|---|
Identifiers | |||||||||
Symbol | CRISPR_assoc | ||||||||
Pfam | PF08798 | ||||||||
Pfam clan | CL0362 | ||||||||
InterPro | IPR010179 | ||||||||
CDD | cd09727 | ||||||||
|
The cas genes in the adaptor and effector modules of the CRISPR-Cas system are believed to have evolved from two different ancestral modules. A transposon-like element called casposon encoding the Cas1-like integrase and potentially other components of the adaptation module was inserted next to the ancestral effector module, which likely functioned as an independent innate immune system.[153] The highly conserved cas1 and cas2 genes of the adaptor module evolved from the ancestral module while a variety of class 1 effector cas genes evolved from the ancestral effector module.[154] The evolution of these various class 1 effector module cas genes was guided by various mechanisms, such as duplication events.[155] On the other hand, each type of class 2 effector module arose from subsequent independent insertions of mobile genetic elements.[156] These mobile genetic elements took the place of the multiple gene effector modules to create single gene effector modules that produce large proteins which perform all the necessary tasks of the effector module.[156] The spacer regions of CRISPR-Cas systems are taken directly from foreign mobile genetic elements and thus their long-term evolution is hard to trace.[157] The non-random evolution of these spacer regions has been found to be highly dependent on the environment and the particular foreign mobile genetic elements it contains.[158]
CRISPR-Cas can immunize bacteria against certain phages and thus halt transmission. For this reason, Koonin described CRISPR-Cas as a Lamarckian inheritance mechanism.[159] However, this was disputed by a critic who noted, "We should remember [Lamarck] for the good he contributed to science, not for things that resemble his theory only superficially. Indeed, thinking of CRISPR and other phenomena as Lamarckian only obscures the simple and elegant way evolution really works".[160] But as more recent studies have been conducted, it has become apparent that the acquired spacer regions of CRISPR-Cas systems are indeed a form of Lamarckian evolution because they are genetic mutations that are acquired and then passed on.[161] On the other hand, the evolution of the Cas gene machinery that facilitates the system evolves through classic Darwinian evolution.[161]
Coevolution
[edit]Analysis of CRISPR sequences revealed coevolution of host and viral genomes.[162]
The basic model of CRISPR evolution is newly incorporated spacers driving phages to mutate their genomes to avoid the bacterial immune response, creating diversity in both the phage and host populations. To resist a phage infection, the sequence of the CRISPR spacer must correspond perfectly to the sequence of the target phage gene. Phages can continue to infect their hosts' given point mutations in the spacer.[152] Similar stringency is required in PAM or the bacterial strain remains phage sensitive.[125][152]
Rates
[edit]A study of 124 S. thermophilus strains showed that 26% of all spacers were unique and that different CRISPR loci showed different rates of spacer acquisition.[124] Some CRISPR loci evolve more rapidly than others, which allowed the strains' phylogenetic relationships to be determined. A comparative genomic analysis showed that E. coli and S. enterica evolve much more slowly than S. thermophilus. The latter's strains that diverged 250,000 years ago still contained the same spacer complement.[163]
Metagenomic analysis of two acid-mine-drainage biofilms showed that one of the analyzed CRISPRs contained extensive deletions and spacer additions versus the other biofilm, suggesting a higher phage activity/prevalence in one community than the other.[81] In the oral cavity, a temporal study determined that 7–22% of spacers were shared over 17 months within an individual while less than 2% were shared across individuals.[133]
From the same environment, a single strain was tracked using PCR primers specific to its CRISPR system. Broad-level results of spacer presence/absence showed significant diversity. However, this CRISPR added three spacers over 17 months,[133] suggesting that even in an environment with significant CRISPR diversity some loci evolve slowly.
CRISPRs were analysed from the metagenomes produced for the Human Microbiome Project.[164] Although most were body-site specific, some within a body site are widely shared among individuals. One of these loci originated from streptococcal species and contained ≈15,000 spacers, 50% of which were unique. Similar to the targeted studies of the oral cavity, some showed little evolution over time.[164]
CRISPR evolution was studied in chemostats using S. thermophilus to directly examine spacer acquisition rates. In one week, S. thermophilus strains acquired up to three spacers when challenged with a single phage.[165] During the same interval, the phage developed single-nucleotide polymorphisms that became fixed in the population, suggesting that targeting had prevented phage replication absent these mutations.[165]
Another S. thermophilus experiment showed that phages can infect and replicate in hosts that have only one targeting spacer. Yet another showed that sensitive hosts can exist in environments with high-phage titres.[166] The chemostat and observational studies suggest many nuances to CRISPR and phage (co)evolution.
Identification
[edit]CRISPRs are widely distributed among bacteria and archaea[91] and show some sequence similarities.[139] Their most notable characteristic is their repeating spacers and direct repeats. This characteristic makes CRISPRs easily identifiable in long sequences of DNA, since the number of repeats decreases the likelihood of a false positive match.[167]
Analysis of CRISPRs in metagenomic data is more challenging, as CRISPR loci do not typically assemble, due to their repetitive nature or through strain variation, which confuses assembly algorithms. Where many reference genomes are available, polymerase chain reaction (PCR) can be used to amplify CRISPR arrays and analyse spacer content.[124][133][168][169][170][171] However, this approach yields information only for specifically targeted CRISPRs and for organisms with sufficient representation in public databases to design reliable polymerase PCR primers. Degenerate repeat-specific primers can be used to amplify CRISPR spacers directly from environmental samples; amplicons containing two or three spacers can be then computationally assembled to reconstruct long CRISPR arrays.[171]
The alternative is to extract and reconstruct CRISPR arrays from shotgun metagenomic data. This is computationally more difficult, particularly with second generation sequencing technologies (e.g. 454, Illumina), as the short read lengths prevent more than two or three repeat units appearing in a single read. CRISPR identification in raw reads has been achieved using purely de novo identification[172] or by using direct repeat sequences in partially assembled CRISPR arrays from contigs (overlapping DNA segments that together represent a consensus region of DNA)[164] and direct repeat sequences from published genomes[173] as a hook for identifying direct repeats in individual reads.
Use by phages
[edit]Another way for bacteria to defend against phage infection is by having chromosomal islands. A subtype of chromosomal islands called phage-inducible chromosomal island (PICI) is excised from a bacterial chromosome upon phage infection and can inhibit phage replication.[174] PICIs are induced, excised, replicated, and finally packaged into small capsids by certain staphylococcal temperate phages. PICIs use several mechanisms to block phage reproduction. In the first mechanism, PICI-encoded Ppi differentially blocks phage maturation by binding or interacting specifically with phage TerS, hence blocking phage TerS/TerL complex formation responsible for phage DNA packaging. In the second mechanism PICI CpmAB redirects the phage capsid morphogenetic protein to make 95% of SaPI-sized capsid and phage DNA can package only 1/3rd of their genome in these small capsids and hence become nonviable phage.[175] The third mechanism involves two proteins, PtiA and PtiB, that target the LtrC, which is responsible for the production of virion and lysis proteins. This interference mechanism is modulated by a modulatory protein, PtiM, binds to one of the interference-mediating proteins, PtiA, and hence achieves the required level of interference.[176]
One study showed that lytic ICP1 phage, which specifically targets Vibrio cholerae serogroup O1, has acquired a CRISPR-Cas system that targets a V. cholera PICI-like element. The system has 2 CRISPR loci and 9 Cas genes. It seems to be homologous to the I-F system found in Yersinia pestis. Moreover, like the bacterial CRISPR-Cas system, ICP1 CRISPR-Cas can acquire new sequences, which allows phage and host to co-evolve.[177][178]
Certain archaeal viruses were shown to carry mini-CRISPR arrays containing one or two spacers. It has been shown that spacers within the virus-borne CRISPR arrays target other viruses and plasmids, suggesting that mini-CRISPR arrays represent a mechanism of heterotypic superinfection exclusion and participate in interviral conflicts.[171]
Applications
[edit]CRISPR gene editing is a revolutionary technology that allows for precise, targeted modifications to the DNA of living organisms. Developed from a natural defense mechanism found in bacteria, CRISPR-Cas9 is the most commonly used system, that allows "cutting" of DNA at specific locations and either delete, modify, or insert genetic material. This technology has transformed fields such as genetics, medicine,[179][180] and agriculture,[181][182] offering potential treatments for genetic disorders, advancements in crop engineering, and research into the fundamental workings of life. However, its ethical implications and potential unintended consequences have sparked significant debate.[183][184]
See also
[edit]- CRISPR activation
- Anti-CRISPR
- CRISPR/Cas Tools
- CRISPR gene editing
- The CRISPR Journal
- "Designer baby"
- DRACO
- Gene knockout
- Genome-wide CRISPR-Cas9 knockout screens
- Glossary of genetics
- Human germline engineering
- Human Nature (2019 documentary film)
- MAGESTIC
- New eugenics
- Prime editing
- RNAi
- SiRNA
- Surveyor nuclease assay
- Synthetic biology
- Zinc finger
Notes
[edit]References
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- ^ Gesner EM, Schellenberg MJ, Garside EL, George MM, Macmillan AM (June 2011). "Recognition and maturation of effector RNAs in a CRISPR interference pathway". Nature Structural & Molecular Biology. 18 (6): 688–692. doi:10.1038/nsmb.2042. PMID 21572444.
- ^ Sashital DG, Jinek M, Doudna JA (June 2011). "An RNA-induced conformational change required for CRISPR RNA cleavage by the endoribonuclease Cse3". Nature Structural & Molecular Biology. 18 (6): 680–687. doi:10.1038/nsmb.2043. PMID 21572442.
- ^ Haurwitz RE, Jinek M, Wiedenheft B, Zhou K, Doudna JA (September 2010). "Sequence- and structure-specific RNA processing by a CRISPR endonuclease". Science. 329 (5997): 1355–1358. Bibcode:2010Sci...329.1355H. doi:10.1126/science.1192272. PMC 3133607. PMID 20829488.
- ^ a b Kunin V, Sorek R, Hugenholtz P (2007). "Evolutionary conservation of sequence and secondary structures in CRISPR repeats". Genome Biology. 8 (4): R61. doi:10.1186/gb-2007-8-4-r61. PMC 1896005. PMID 17442114.
- ^ Carte J, Wang R, Li H, Terns RM, Terns MP (December 2008). "Cas6 is an endoribonuclease that generates guide RNAs for invader defense in prokaryotes". Genes & Development. 22 (24): 3489–3496. doi:10.1101/gad.1742908. PMC 2607076. PMID 19141480.
- ^ Wang R, Preamplume G, Terns MP, Terns RM, Li H (February 2011). "Interaction of the Cas6 riboendonuclease with CRISPR RNAs: recognition and cleavage". Structure. 19 (2): 257–264. doi:10.1016/j.str.2010.11.014. PMC 3154685. PMID 21300293.
- ^ Niewoehner O, Jinek M, Doudna JA (January 2014). "Evolution of CRISPR RNA recognition and processing by Cas6 endonucleases". Nucleic Acids Research. 42 (2): 1341–1353. doi:10.1093/nar/gkt922. PMC 3902920. PMID 24150936.
- ^ Semenova E, Jore MM, Datsenko KA, Semenova A, Westra ER, Wanner B, et al. (June 2011). "Interference by clustered regularly interspaced short palindromic repeat (CRISPR) RNA is governed by a seed sequence". Proceedings of the National Academy of Sciences of the United States of America. 108 (25): 10098–10103. Bibcode:2011PNAS..10810098S. doi:10.1073/pnas.1104144108. PMC 3121866. PMID 21646539.
- ^ Gudbergsdottir S, Deng L, Chen Z, Jensen JV, Jensen LR, She Q, et al. (January 2011). "Dynamic properties of the Sulfolobus CRISPR/Cas and CRISPR/Cmr systems when challenged with vector-borne viral and plasmid genes and protospacers". Molecular Microbiology. 79 (1): 35–49. doi:10.1111/j.1365-2958.2010.07452.x. PMC 3025118. PMID 21166892.
- ^ Manica A, Zebec Z, Teichmann D, Schleper C (April 2011). "In vivo activity of CRISPR-mediated virus defence in a hyperthermophilic archaeon". Molecular Microbiology. 80 (2): 481–491. doi:10.1111/j.1365-2958.2011.07586.x. PMID 21385233.
- ^ Jore MM, Lundgren M, van Duijn E, Bultema JB, Westra ER, Waghmare SP, et al. (May 2011). "Structural basis for CRISPR RNA-guided DNA recognition by Cascade". Nature Structural & Molecular Biology. 18 (5): 529–536. doi:10.1038/nsmb.2019. PMID 21460843.
- ^ Wiedenheft B, Lander GC, Zhou K, Jore MM, Brouns SJ, van der Oost J, et al. (September 2011). "Structures of the RNA-guided surveillance complex from a bacterial immune system". Nature. 477 (7365): 486–489. Bibcode:2011Natur.477..486W. doi:10.1038/nature10402. PMC 4165517. PMID 21938068.
- ^ Zhang J, Rouillon C, Kerou M, Reeks J, Brugger K, Graham S, et al. (February 2012). "Structure and mechanism of the CMR complex for CRISPR-mediated antiviral immunity". Molecular Cell. 45 (3): 303–313. doi:10.1016/j.molcel.2011.12.013. PMC 3381847. PMID 22227115.
- ^ a b Hale CR, Zhao P, Olson S, Duff MO, Graveley BR, Wells L, et al. (November 2009). "RNA-guided RNA cleavage by a CRISPR RNA-Cas protein complex". Cell. 139 (5): 945–956. doi:10.1016/j.cell.2009.07.040. PMC 2951265. PMID 19945378.
- ^ Estrella MA, Kuo FT, Bailey S (2016). "RNA-activated DNA cleavage by the Type III-B CRISPR–Cas effector complex". Genes & Development. 30 (4): 460–470. doi:10.1101/gad.273722.115. PMC 4762430. PMID 26848046.
- ^ Samai P, Pyenson N, Jiang W, Goldberg GW, Hatoum-Aslan A, Marraffini LA (2015). "Co-transcriptional DNA and RNA Cleavage during Type III CRISPR-Cas Immunity". Cell. 161 (5): 1164–1174. doi:10.1016/j.cell.2015.04.027. PMC 4594840. PMID 25959775.
- ^ a b c Marraffini LA, Sontheimer EJ (January 2010). "Self versus non-self discrimination during CRISPR RNA-directed immunity". Nature. 463 (7280): 568–571. Bibcode:2010Natur.463..568M. doi:10.1038/nature08703. PMC 2813891. PMID 20072129.
- ^ Krupovic M, Béguin P, Koonin EV (August 2017). "Casposons: mobile genetic elements that gave rise to the CRISPR-Cas adaptation machinery". Current Opinion in Microbiology. 38: 36–43. doi:10.1016/j.mib.2017.04.004. PMC 5665730. PMID 28472712.
- ^ Koonin EV, Makarova KS (May 2013). "CRISPR-Cas: evolution of an RNA-based adaptive immunity system in prokaryotes". RNA Biology. 10 (5): 679–686. doi:10.4161/rna.24022. PMC 3737325. PMID 23439366.
- ^ Koonin EV, Makarova KS, Zhang F (June 2017). "Diversity, classification and evolution of CRISPR-Cas systems". Current Opinion in Microbiology. 37: 67–78. doi:10.1016/j.mib.2017.05.008. PMC 5776717. PMID 28605718.
- ^ a b Shmakov S, Smargon A, Scott D, Cox D, Pyzocha N, Yan W, et al. (March 2017). "Diversity and evolution of class 2 CRISPR-Cas systems". Nature Reviews. Microbiology. 15 (3): 169–182. doi:10.1038/nrmicro.2016.184. PMC 5851899. PMID 28111461.
- ^ Kupczok A, Bollback JP (February 2013). "Probabilistic models for CRISPR spacer content evolution". BMC Evolutionary Biology. 13 (1): 54. Bibcode:2013BMCEE..13...54K. doi:10.1186/1471-2148-13-54. PMC 3704272. PMID 23442002.
- ^ Sternberg SH, Richter H, Charpentier E, Qimron U (March 2016). "Adaptation in CRISPR-Cas Systems". Molecular Cell. 61 (6): 797–808. doi:10.1016/j.molcel.2016.01.030. hdl:21.11116/0000-0003-E74E-2. PMID 26949040.
- ^ Koonin EV, Wolf YI (November 2009). "Is evolution Darwinian or/and Lamarckian?". Biology Direct. 4: 42. doi:10.1186/1745-6150-4-42. PMC 2781790. PMID 19906303.
- ^ Weiss A (October 2015). "Lamarckian Illusions". Trends in Ecology & Evolution. 30 (10): 566–568. Bibcode:2015TEcoE..30..566W. doi:10.1016/j.tree.2015.08.003. PMID 26411613.
- ^ a b Koonin EV, Wolf YI (February 2016). "Just how Lamarckian is CRISPR-Cas immunity: the continuum of evolvability mechanisms". Biology Direct. 11 (1): 9. doi:10.1186/s13062-016-0111-z. PMC 4765028. PMID 26912144.
- ^ Heidelberg JF, Nelson WC, Schoenfeld T, Bhaya D (2009). Ahmed N (ed.). "Germ warfare in a microbial mat community: CRISPRs provide insights into the co-evolution of host and viral genomes". PLOS ONE. 4 (1): e4169. Bibcode:2009PLoSO...4.4169H. doi:10.1371/journal.pone.0004169. PMC 2612747. PMID 19132092.
- ^ Touchon M, Rocha EP (June 2010). Randau L (ed.). "The small, slow and specialized CRISPR and anti-CRISPR of Escherichia and Salmonella". PLOS ONE. 5 (6): e11126. Bibcode:2010PLoSO...511126T. doi:10.1371/journal.pone.0011126. PMC 2886076. PMID 20559554.
- ^ a b c Rho M, Wu YW, Tang H, Doak TG, Ye Y (2012). "Diverse CRISPRs evolving in human microbiomes". PLOS Genetics. 8 (6): e1002441. doi:10.1371/journal.pgen.1002441. PMC 3374615. PMID 22719260.
- ^ a b Sun CL, Barrangou R, Thomas BC, Horvath P, Fremaux C, Banfield JF (February 2013). "Phage mutations in response to CRISPR diversification in a bacterial population". Environmental Microbiology. 15 (2): 463–470. Bibcode:2013EnvMi..15..463S. doi:10.1111/j.1462-2920.2012.02879.x. PMID 23057534.
- ^ Kuno S, Sako Y, Yoshida T (May 2014). "Diversification of CRISPR within coexisting genotypes in a natural population of the bloom-forming cyanobacterium Microcystis aeruginosa". Microbiology. 160 (Pt 5): 903–916. doi:10.1099/mic.0.073494-0. PMID 24586036.
- ^ Sorek R, Kunin V, Hugenholtz P (March 2008). "CRISPR—a widespread system that provides acquired resistance against phages in bacteria and archaea". Nature Reviews. Microbiology. 6 (3): 181–186. doi:10.1038/nrmicro1793. PMID 18157154.
Table 1: Web resources for CRISPR analysis
- ^ Pride DT, Salzman J, Relman DA (September 2012). "Comparisons of clustered regularly interspaced short palindromic repeats and viromes in human saliva reveal bacterial adaptations to salivary viruses". Environmental Microbiology. 14 (9): 2564–2576. Bibcode:2012EnvMi..14.2564P. doi:10.1111/j.1462-2920.2012.02775.x. PMC 3424356. PMID 22583485.
- ^ Held NL, Herrera A, Whitaker RJ (November 2013). "Reassortment of CRISPR repeat-spacer loci in Sulfolobus islandicus". Environmental Microbiology. 15 (11): 3065–3076. Bibcode:2013EnvMi..15.3065H. doi:10.1111/1462-2920.12146. PMID 23701169.
- ^ Held NL, Herrera A, Cadillo-Quiroz H, Whitaker RJ (September 2010). "CRISPR associated diversity within a population of Sulfolobus islandicus". PLOS ONE. 5 (9): e12988. Bibcode:2010PLoSO...512988H. doi:10.1371/journal.pone.0012988. PMC 2946923. PMID 20927396.
- ^ a b c Medvedeva S, Liu Y, Koonin EV, Severinov K, Prangishvili D, Krupovic M (November 2019). "Virus-borne mini-CRISPR arrays are involved in interviral conflicts". Nature Communications. 10 (1): 5204. Bibcode:2019NatCo..10.5204M. doi:10.1038/s41467-019-13205-2. PMC 6858448. PMID 31729390.
- ^ Skennerton CT, Imelfort M, Tyson GW (May 2013). "Crass: identification and reconstruction of CRISPR from unassembled metagenomic data". Nucleic Acids Research. 41 (10): e105. doi:10.1093/nar/gkt183. PMC 3664793. PMID 23511966.
- ^ Stern A, Mick E, Tirosh I, Sagy O, Sorek R (October 2012). "CRISPR targeting reveals a reservoir of common phages associated with the human gut microbiome". Genome Research. 22 (10): 1985–1994. doi:10.1101/gr.138297.112. PMC 3460193. PMID 22732228.
- ^ Novick RP, Christie GE, Penadés JR (August 2010). "The phage-related chromosomal islands of Gram-positive bacteria". Nature Reviews Microbiology. 8 (8): 541–551. doi:10.1038/nrmicro2393. PMC 3522866. PMID 20634809.
- ^ Ram G, Chen J, Kumar K, Ross HF, Ubeda C, Damle PK, et al. (October 2012). "Staphylococcal pathogenicity island interference with helper phage reproduction is a paradigm of molecular parasitism". Proceedings of the National Academy of Sciences of the United States of America. 109 (40): 16300–16305. Bibcode:2012PNAS..10916300R. doi:10.1073/pnas.1204615109. PMC 3479557. PMID 22991467.
- ^ Ram G, Chen J, Ross HF, Novick RP (October 2014). "Precisely modulated pathogenicity island interference with late phage gene transcription". Proceedings of the National Academy of Sciences of the United States of America. 111 (40): 14536–14541. Bibcode:2014PNAS..11114536R. doi:10.1073/pnas.1406749111. PMC 4209980. PMID 25246539.
- ^ Seed KD, Lazinski DW, Calderwood SB, Camilli A (February 2013). "A bacteriophage encodes its own CRISPR/Cas adaptive response to evade host innate immunity". Nature. 494 (7438): 489–491. Bibcode:2013Natur.494..489S. doi:10.1038/nature11927. PMC 3587790. PMID 23446421.
- ^ Boyd CM, Angermeyer A, Hays SG, Barth ZK, Patel KM, Seed KD (September 2021). "Bacteriophage ICP1: A Persistent Predator of Vibrio cholerae". Annual Review of Virology. 8 (1): 285–304. doi:10.1146/annurev-virology-091919-072020. ISSN 2327-056X. PMC 9040626. PMID 34314595.
- ^ Feng Q, Li Q, Zhou H, Wang Z, Lin C, Jiang Z, et al. (August 2024). "CRISPR technology in human diseases". Medcomm. 5 (8): e672. doi:10.1002/mco2.672. PMC 11286548. PMID 39081515.
- ^ Li T, Li S, Kang Y, Zhou J, Yi M (August 2024). "Harnessing the evolving CRISPR/Cas9 for precision oncology". Journal of Translational Medicine. 22 (1): 749. doi:10.1186/s12967-024-05570-4. PMC 11312220. PMID 39118151.
- ^ Mishra S, Nayak S, Tuteja N, Poosapati S, Swain DM, Sahoo RK (July 2024). "CRISPR/Cas-Mediated Genome Engineering in Plants: Application and Prospectives". Plants. 13 (14). Basel, Switzerland: 1884. doi:10.3390/plants13141884. PMC 11279650. PMID 39065411.
- ^ Kaur R, Gupta S, Chauhan A, Mishra V, Sharma MK, Singh J (August 2024). "Harnessing the power of clustered regularly interspaced short palindromic repeats (CRISPR) based microfluidics for next-generation molecular diagnostics". Molecular Biology Reports. 51 (1): 896. doi:10.1007/s11033-024-09840-8. PMID 39115550.
- ^ Shinwari ZK, Tanveer F, Khalil AT (2018). "Ethical Issues Regarding CRISPR Mediated Genome Editing". Current Issues in Molecular Biology. 26: 103–110. doi:10.21775/cimb.026.103. PMID 28879860.
- ^ Kozan DW, Farber SA (February 2024). "Is It Ever Wise to Edit Wild-Type Alleles? Engineered CRISPR Alleles Versus Millions of Years of Human Evolution". Arteriosclerosis, Thrombosis, and Vascular Biology. 44 (2): 328–333. doi:10.1161/ATVBAHA.123.318069. PMC 10948015. PMID 38059350.
Further reading
[edit]- Doudna J, Mali P (23 March 2016). CRISPR-Cas: A Laboratory Manual. New York: Cold Spring Harbor Laboratory Press. ISBN 978-1-62182-131-1.
- Mohanraju P, Makarova KS, Zetsche B, Zhang F, Koonin EV, van der Oost J (August 2016). "Diverse evolutionary roots and mechanistic variations of the CRISPR-Cas systems". Science. 353 (6299): aad5147. doi:10.1126/science.aad5147. hdl:1721.1/113195. PMID 27493190.
- Sander JD, Joung JK (April 2014). "CRISPR-Cas systems for editing, regulating and targeting genomes". Nature Biotechnology. 32 (4): 347–355. doi:10.1038/nbt.2842. PMC 4022601. PMID 24584096.
- Slaymaker IM, Gao L, Zetsche B, Scott DA, Yan WX, Zhang F (January 2016). "Rationally engineered Cas9 nucleases with improved specificity". Science. 351 (6268): 84–88. Bibcode:2016Sci...351...84S. doi:10.1126/science.aad5227. PMC 4714946. PMID 26628643.
- Terns RM, Terns MP (March 2014). "CRISPR-based technologies: prokaryotic defense weapons repurposed". Trends in Genetics. 30 (3): 111–118. doi:10.1016/j.tig.2014.01.003. PMC 3981743. PMID 24555991.
- Westra ER, Buckling A, Fineran PC (May 2014). "CRISPR-Cas systems: beyond adaptive immunity". Nature Reviews Microbiology. 12 (5): 317–326. doi:10.1038/nrmicro3241. PMID 24704746.
- Andersson AF, Banfield JF (May 2008). "Virus population dynamics and acquired virus resistance in natural microbial communities". Science. 320 (5879): 1047–1050. Bibcode:2008Sci...320.1047A. doi:10.1126/science.1157358. PMID 18497291.
- Hale C, Kleppe K, Terns RM, Terns MP (December 2008). "Prokaryotic silencing (psi)RNAs in Pyrococcus furiosus". RNA. 14 (12): 2572–2579. doi:10.1261/rna.1246808. PMC 2590957. PMID 18971321.
- van der Ploeg JR (June 2009). "Analysis of CRISPR in Streptococcus mutans suggests frequent occurrence of acquired immunity against infection by M102-like bacteriophages". Microbiology. 155 (Pt 6): 1966–1976. doi:10.1099/mic.0.027508-0. PMID 19383692.
- van der Oost J, Brouns SJ (November 2009). "RNAi: prokaryotes get in on the act". Cell. 139 (5): 863–865. doi:10.1016/j.cell.2009.11.018. PMID 19945373.
- Karginov FV, Hannon GJ (January 2010). "The CRISPR system: small RNA-guided defense in bacteria and archaea". Molecular Cell. 37 (1): 7–19. doi:10.1016/j.molcel.2009.12.033. PMC 2819186. PMID 20129051.
- Pul U, Wurm R, Arslan Z, Geissen R, Hofmann N, Wagner R (March 2010). "Identification and characterization of E. coli CRISPR-cas promoters and their silencing by H-NS". Molecular Microbiology. 75 (6): 1495–1512. doi:10.1111/j.1365-2958.2010.07073.x. PMID 20132443.
- Díez-Villaseñor C, Almendros C, García-Martínez J, Mojica FJ (May 2010). "Diversity of CRISPR loci in Escherichia coli". Microbiology. 156 (Pt 5): 1351–1361. doi:10.1099/mic.0.036046-0. PMID 20133361.
- Deveau H, Garneau JE, Moineau S (2010). "CRISPR/Cas system and its role in phage-bacteria interactions". Annual Review of Microbiology. 64: 475–493. doi:10.1146/annurev.micro.112408.134123. PMID 20528693.
- Koonin EV, Makarova KS (December 2009). "CRISPR-Cas: an adaptive immunity system in prokaryotes". F1000 Biology Reports. 1: 95. doi:10.3410/B1-95. PMC 2884157. PMID 20556198.
- "The age of the red pen". The Economist. August 22, 2015. ISSN 0013-0613. Archived from the original on 2015-08-24. Retrieved 2015-08-25.
- Ran AF, Hsu PD, Wright J, Agarwala V, Scott DA, Zhang F (2013). "Genome engineering using the CRISPR-Cas9 system". Nature Protocols. 8 (11): 2281–2308. doi:10.1038/nprot.2013.143. PMC 3969860. PMID 24157548.
External links
[edit]- "Advanced Gene Editing: CRISPR-Cas9" (PDF). Congressional Research Service.
- "Jennifer Doudna talk: Genome Engineering with CRISPR-Cas9: Birth of a Breakthrough Technology". 10 September 2022.
- "Human Nature". NOVA. Season 47. Episode 9. September 9, 2020. PBS. WGBH. Retrieved April 7, 2023.
Protein Data Bank
[edit]- Overview of all the structural information available in the PDB for UniProt: Q46901 (CRISPR system Cascade subunit CasA) at the PDBe-KB.
- Overview of all the structural information available in the PDB for UniProt: P76632 (CRISPR system Cascade subunit CasB) at the PDBe-KB.
- Overview of all the structural information available in the PDB for UniProt: Q46899 (CRISPR system Cascade subunit CasC) at the PDBe-KB.
- Overview of all the structural information available in the PDB for UniProt: Q46898 (CRISPR system Cascade subunit CasD) at the PDBe-KB.
- Overview of all the structural information available in the PDB for UniProt: Q46897 (CRISPR system Cascade subunit CasE) at the PDBe-KB.