The nuclear poly(A) binding protein of mammals, but not of fission yeast, participates in mRNA polyadenylation.
The nuclear poly(A) binding protein (PABPN1) has been suggested, on the basis of biochemical evidence, to play a role in mRNA polyadenylation by strongly increasing the processivity of poly(A) polymerase. While experiments in metazoans have tended to support such a role, the results were not unequivocal, and genetic data show that the S. pombe ortholog of PABPN1, Pab2, is not involved in mRNA polyadenylation. The specific model in which PABPN1 increases the rate of poly(A) tail elongation has never been examined in vivo. Here, we have used 4-thiouridine pulse-labeling to examine the lengths of newly synthesized poly(A) tails in human cells. Knockdown of PABPN1 strongly reduced the synthesis of full-length tails of ∼250 nucleotides, as predicted from biochemical data. We have also purified S. pombe Pab2 and the S. pombe poly(A) polymerase, Pla1, and examined their in vitro activities. Whereas PABPN1 strongly increases the activity of its cognate poly(A) polymerase in vitro, Pab2 was unable to stimulate Pla1 to any significant extent. Thus, in vitro and in vivo data are consistent in supporting a role of PABPN1 but not S. pombe Pab2 in the polyadenylation of mRNA precursors.
['Kühn|Uwe|U|', 'Buschmann|Juliane|J|', 'Wahle|Elmar|E|0000-0003-2504-0677']
D003001:Cloning, Molecular D004926:Escherichia coli D015870:Gene Expression D005786:Gene Expression Regulation D057809:HEK293 Cells D006801:Humans D007527:Isoenzymes D011061:Poly A D039122:Poly(A)-Binding Protein I D039102:Poly(A)-Binding Proteins D026723:Polyadenylation D011062:Polynucleotide Adenylyltransferase D012322:RNA Precursors D012333:RNA, Messenger D011994:Recombinant Proteins D012568:Schizosaccharomyces D029702:Schizosaccharomyces pombe Proteins D013045:Species Specificity D013379:Substrate Specificity
poly(A) binding protein mRNA polyadenylation processing poly(A) polymerase pre-mRNA 3′