Poly A Binding Protein Cytoplasmic 1 (PABPC1)

The poly(A)-binding protein (PABP), which is found complexed to the 3-prime poly(A) tail of eukaryotic mRNA, is required for poly(A) shortening and translation initiation. In humans, the PABPs comprise a small nuclear isoform and a conserved gene family that displays at least 3 functional proteins: PABP1 (PABPC1), inducible PABP (iPABP, or PABPC4), and PABP3 (PABPC3). In addition, there are at least 4 pseudogenes, PABPCP1 to PABPCP4.The predicted 633-amino acid protein contains 4 repeats of an approximately 80-amino acid unit in its N-terminal half. The authors found that this repeat region is highly conserved between human and yeast PABP and is sufficient for poly(A) binding. In vitro translation of the human PABP cDNA yielded a protein with an apparent molecular mass of 73 kD by SDS-PAGE.