title: Alterations of activities of ribonucleases and polyadenylate polymerase in synchronized mouse L cells.
abstract: The activities of the three known catabolic and the one anabolic polyadenylate enzymes have been determined in synchronized L5178y cells: endoribonuclease, exoribonuclease, 5'-nucleotidase and poly(A) polymerase (Mg2+-dependent). These four enzymes were found primarily in the nuclear fraction. The activity of poly(A) polymerase remains essentially constant during the transition from G1 to S phase. However, the poly(A) catabolic enzyme activities increase parallel with DNA synthesis; the endoribonuclease activity increases 4-fold during G1 to S phase, the exoribonuclease and the nucleotidase activities increasing 30-fold and 16-fold. During the S phase the poly(A)-degrading enzymes are far more active than the poly(A)-synthesizing activity of poly(A) polymerase. We conclude that in L5178y cells the poly(A)-degrading enzymes probably function in regulation of the post-transcriptional net-polyadenylation of heterogeneous nuclear RNA during the phase of DNA synthesis.
mesh_terms: D002455:Cell Division; D002460:Cell Line; D007700:Kinetics; D007739:L Cells / Q000378:metabolism*; D008938:Mitosis; D008970:Molecular Weight; D009713:Nucleotidyltransferases / Q000378:metabolism*; D011062:Polynucleotide Adenylyltransferase / Q000378:metabolism*; D012260:Ribonucleases / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013997:Time Factors
chemical_list: D009713:Nucleotidyltransferases; D011062:Polynucleotide Adenylyltransferase; D012260:Ribonucleases