title: Cellular regulation of poly ADP-ribosylation of proteins. II. Augmentation of poly(ADP-ribose) polymerase in SV40 3T3 cells following methotrexate-induced G1/S inhibition of cell cycle progression.
abstract: SV40-3T3 cells were exposed in monolayer cultures to 5 X 10(-7) M methotrexate (MTX), that inhibited thymidylate synthetase, arrested cell growth without cell killing in 24 h and did not induce single- (ss) or double-strand (ds) breaks in DNA. Following 24, up to 72 h, the poly(ADP-ribose) polymerase content of attached cells was induced by 5 X 10(-7) M MTX and the augmentation of the enzyme increased with the time of exposure to the drug. Inhibition of protein or RNA synthesis abolished augmentation of enzymatic activity; so too did the initiation of maximal cell growth by thymidine + hypoxanthine, by-passing the inhibitory site of MTX. Isolation of the ADP-ribosylated enzyme protein by gel electrophoresis identified poly(ADP-ribose) polymerase protein as the molecule that was induced by 5 X 10(-7) M MTX. Under identical conditions, the poly(ADP-ribose) polymerase induction in 3T3 cells could not be demonstrated. A possible cell-cycle-dependent biosynthesis of the enzyme protein is proposed in SV40 3T3 cells.
mesh_terms: D000818:Animals; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D007399:Interphase / Q000187:drug effects; D007700:Kinetics; D008727:Methotrexate / Q000494:pharmacology*; D051379:Mice; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D013539:Simian virus 40 / Q000235:genetics*
chemical_list: D011506:Proteins; D011065:Poly(ADP-ribose) Polymerases; D008727:Methotrexate