Multiple forms of poly(A) polymerases in human cells
1994 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 91, no 3, 979-983 p.Article in journal (Refereed) Published
We have cloned human poly(A) polymerase (PAP) mRNA as cDNA in Escherichia coli. The primary structure of the mRNA was determined and compared to the bovine PAP mRNA sequence. The two sequences were 97% identical at the nucleotide level, which translated into 99% similarity at the amino acid level. Polypeptides representing recombinant PAP were expressed in E. coli, purified, and used as antigens to generate monoclonal antibodies. Western blot analysis using these monoclonal antibodies as probes revealed three PAPs, having estimated molecular masses of 90, 100, and 106 kDa in HeLa cell extracts. Fractionation of HeLa cells showed that the 90-kDa polypeptide was nuclear while the 100- and 106-kDa species were present in both nuclear and cytoplasmic fractions. The 106-kDa PAP was most likely a phosphorylated derivative of the 100-kDa species. PAP activity was recovered in vitro by using purified recombinant human PAP. Subsequent mutational analysis revealed that both the N- and C-terminal regions of PAP were important for activity and suggested that cleavage and polyadenylylation specificity factor (CPSF) interacted with the C-terminal region of PAP. Interestingly, tentative phosphorylation sites have been identified in this region, suggesting that phosphorylation/dephosphorylation may regulate the interaction between the two polyadenylylation factors PAP and CPSF.
Place, publisher, year, edition, pages
1994. Vol. 91, no 3, 979-983 p.
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:uu:diva-102236DOI: 10.1073/pnas.91.3.979ISI: A1994MV27800033PubMedID: 8302877OAI: oai:DiVA.org:uu-102236DiVA: diva2:214542