Insertion sequence: Difference between revisions
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An '''insertion sequence''' (also known as an '''IS''', an '''insertion sequence element''', or an '''IS element''') is a short [[DNA]] sequence that acts as a simple [[transposon|transposable element]]. Insertion sequences have two major characteristics: they are small relative to other transposable elements (generally around 700 to 2500 [[base pair|bp]] in length) and only code for proteins implicated in the [[Transposable element|transposition]] activity (they are thus different from other [[transposons]], which also carry accessory genes such as antibiotic resistance genes). These proteins are usually the [[transposase]] which catalyses the enzymatic reaction allowing the IS to move, and also one regulatory protein which either stimulates or inhibits the transposition activity. The coding region in an insertion sequence is usually flanked by [[inverted repeat]]s. For example, the well-known IS''911'' (1250 bp) is flanked by two 36bp inverted repeat extremities and the coding region has two genes partially overlapping ''orfA'' and ''orfAB'', coding the transposase (OrfAB) and a regulatory protein (OrfA). [http://www-is.biotoul.fr/is/IS_infos/IS3_family.html#IS911] |
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A particular insertion sequence may be named according to the form IS''n'', where ''n'' is a [[natural number|number]] (e.g. IS''1'', IS''2'', IS''3'', IS''10'', IS''50'', IS''911'', IS''26'' etc.); this is not the only naming scheme used, however. Although insertion sequences are usually discussed in the context of [[prokaryote|prokaryotic]] [[genome]]s, certain [[eukaryote|eukaryotic]] DNA sequences belonging to the family of Tc1/''mariner'' transposable elements may be considered to be, insertion sequences. [http://mmbr.asm.org/cgi/content/full/62/3/725#SEC6] |
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[[Image:Composite transposon.svg|thumbnail|Diagram illustrating the role of insertion sequences ("IS") in a composite transposon]] |
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In addition to occurring autonomously, insertion sequences may also occur as parts of [[composite transposon]]s; in a composite transposon, two insertion sequences flank one or more accessory genes, such as an antibiotic resistance gene (e.g. [[Tn10]], Tn''5''). Nevertheless, there exist another sort of transposons, called unit transposons, that do not carry insertion sequences at their extremities (e.g. Tn''7''). |
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A complex transposon does not rely on flanking insertion sequences for resolvase. The resolvase is part of the tns genome and cuts at flanking inverted repeats. |
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==See also== |
==See also== |
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Revision as of 17:54, 17 April 2017
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See also
References
- Campbell, Neil A. and Reece, Jane B. (2002). Biology (6th ed.), pp. 345–346. San Francisco: Benjamin Cummings. ISBN 0-8053-6624-5.
- Mahillon, Jacques and Chandler, Michael (1998). "Insertion sequences". Microbiology and Molecular Biology Reviews 62 (3), 725-774. Retrieved January 11, 2006.
- Prescott, Lansing M.; Harley, John P.; and Klein, Donald A. (2002). Microbiology (5th ed.), pp. 298–299. New York: McGraw-Hill. ISBN 0-07-232041-9.
- Shuler, Michael L. and Kargi, Fikret (2002). Bioprocess Engineering: Basic Concepts (2nd ed.), p. 220. Upper Saddle River, NJ: Prentice Hall PTR. ISBN 0-13-081908-5.