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Poly(A)-binding protein

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Poly(A) RNA Binding Protein PABP, PDB 1CVJ

Poly(A)-binding protein (PAB or PABP)[1] is a RNA-binding protein which binds to the poly(A) tail of mRNA.[2] The poly(A) tail is located on the 3' end of mRNA and is 200-250 nucleotides long. The binding protein is also involved in mRNA precursors by helping Polyadenylate polyermase add the Poly(A) nucleotide tail to the pre-mRNA before translation.[3] The nuclear isoform selectively binds to around 50 nucleotides and stimulates the activity of Polyadenylate polymerase by increasing its affinity towards RNA. Poly(A)-binding protein is also present during stages of mRNA metabolism including Nonsense-mediated decay and nucleocytoplasmic trafficking. The poly(A)-binding protein may also protect the tail from degradation and regulate mRNA production. Without these two proteins in-tandem, then the poly(A) tail would not be added and the RNA would degrade quickly.[4]

Expression and binding

The expression of mammalian Poly(A)-binding protein is regulated at the translational level by a feed-back mechanism: the mRNA encoding PABP contains in its 5' UTR an A-rich sequence which binds Poly(A)-binding protein. This leads to autoregulatory repression of translation of PABP.

The cytosolic isoform of eukaryotes' Poly(A) binding protein binds to the initiation factor eIF-4G via its C-terminal domain. EIF-4G is bound to eIF-4E, another initiation factor bound to the 5' cap on the 5' end of mRNA. This binding forms the characteristic loop structure of eukaryotic protein synthesis. Poly(A)-binding protein interacting proteins in the cytosol compete for the eIF-4G binding sites. Poly(A)-binding protein has also been shown to interact with a termination factor (eRF3)

Rotavirus NSP3

Cellular vs Rotavirus Translation

Rotavirus RNA-binding protein NSP3 interacts with eIF4GI and evicts the poly(A) binding protein from eIF4F. And NSP3A, by taking the place of PABP on eIF4GI, is responsible for the shut-off of cellular protein synthesis.[5]

Genes

There are several forms.[6] These include:

References

  1. ^ Kahvejian A, Svitkin YV, Sukarieh R, M'Boutchou MN, Sonenberg N (January 2005). "Mammalian poly(A)-binding protein is a eukaryotic translation initiation factor, which acts via multiple mechanisms". Genes Dev. 19 (1): 104–13. doi:10.1101/gad.1262905. PMC 540229. PMID 15630022.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  2. ^ Poly(A)-Binding+Proteins at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
  3. ^ "UniProtKB - Q86U42 (PABP2_HUMAN)". uniprot.org. Retrieved 17 November 2015.
  4. ^ Voet, Donald; Voet, Judith. Biochemistry (4 ed.). Wiley. p. 1304.
  5. ^ Piron, M; Vende, P; Cohen, J; Poncet, D (1998). "Rotavirus RNA-binding protein NSP3 interacts with eIF4GI and evicts the poly(A) binding protein from eIF4F" (Free full text). The EMBO Journal. 17 (19): 5811–21. doi:10.1093/emboj/17.19.5811. PMC 1170909. PMID 9755181.
  6. ^ Katzenellenbogen RA, Vliet-Gregg P, Xu M, Galloway DA (December 2010). "Cytoplasmic Poly(A) Binding Proteins Regulate Telomerase Activity and Cell Growth in Human Papillomavirus Type 16 E6-Expressing Keratinocytes". J. Virol. 84 (24): 12934–44. doi:10.1128/JVI.01377-10. PMC 3004306. PMID 20943973.{{cite journal}}: CS1 maint: multiple names: authors list (link)


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