Poly(A)-binding protein (PAB or PABP) is a RNA-binding protein which binds to the poly(A) tail of mRNA. The poly(A) tail is located on the 3' end of mRNA. The nuclear isoforms selectively binds to around 50 nucleotides and stimulates the activity of Polyadenylate polymerase.
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 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.
There are several forms. These include:
- 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.
- Poly(A)-Binding Proteins at the US National Library of Medicine Medical Subject Headings (MeSH)
- 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.
- 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.
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