ISOLATION OF GENOMIC AND CDNA CLONES ENCODING BOVINE POLY(A)-BINDING-PROTEIN-II

cDNA clones for bovine poly(A) binding protein II (PAB II) were isolat ed. Their sequence predicts a protein of 32.8 kDa, revising earlier es timates of molecular mass, The protein contains one putative RNA-bindi ng domain of the RNP type, an acidic N-terminal and a basic C-terminal domain, Analyses of authentic PAB II were in good agreement with all predictions from the cDNA sequence except that a number of arginine re sidues appeared to be post-translationally modified. Poly(A) binding p rotein Il expressed in Escherichia coli was active in poly(A) binding and reconstitution of processive polyadenylation, including poly(A) ta il length control, The cDNA clones showed a number of potential PAB II binding sites in the 3' untranslated sequence. Bovine poly(A)(+) RNA contained two mRNAs hybridizing to a PAB II-specific probe, Analysis o f a genomic clone revealed six introns in the coding sequence. The rev ised molecular mass led to a demonstration of PAB II oligomer formatio n and a reinterpretation of earlier data concerning the protein's bind ing to poly(A).