Poly(A)-binding protein

File:RABP.PNG

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

Poly(A)-binding protein 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 nucleur isoforms selectively binds to around 50 nucleotides and stimulates the activity of Polyadenylate polymerase.

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 repression of translation

THe cytosolic isoform of eukaryotes Poly(A) binding protein binds to the intiation 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

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.

Cellular vs Rotavirus Translation

Genes

• PABPC1, PABPC3, PABPC4, PABPC5

External links

• Poly(A)-Binding+Proteins at the U.S. National Library of Medicine Medical Subject Headings (MeSH)