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Poly(A)-binding protein
RNA binding protein / From Wikipedia, the free encyclopedia
Poly(A)-binding protein (PAB or PABP)[1] is an RNA-binding protein which triggers the binding of eukaryotic initiation factor 4 complex (eIF4G) directly to the poly(A) tail of mRNA which is 200-250 nucleotides long.[2] The poly(A) tail is located on the 3' end of mRNA and was discovered by Mary Edmonds,[3] who also characterized the poly-A polymerase enzyme that generates the poly(a) tail.[4] The binding protein is also involved in mRNA precursors by helping polyadenylate polymerase add the poly(A) nucleotide tail to the pre-mRNA before translation.[5] 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.[6]
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