title: NAD+, ADP-ribosylation and transcription in permeabilized mammalian cells.
abstract: When permeabilized hamster fibroblasts were incubated with 4 mM-NAD+, the substrate for poly(ADP-ribose) polymerase, RNA polymerase I activity was inhibited by about 85%. This inhibition was not relieved by prior incubation of cells with 3-aminobenzamide, a potent inhibitor of the poly(ADP-ribose) polymerase. Digestion of cells with pancreatic deoxyribonuclease I resulted in the inhibition of RNA polymerase I by 80% and the activation of poly(ADP-ribose) polymerase by up to 300%; prior incubation with 3-aminobenzamide did not prevent the inhibition of the RNA polymerase activity. No radioactivity was found associated with RNA polymerase I during later stages of purification of this enzyme from permeabilized cells previously incubated with [14C]NAD+. The inhibitory effect of NAD+ on RNA polymerase I was not specific for NAD+, as other small, negatively charged molecules with a nuclear location also inhibited the enzyme. The results do not support the concept of a role for ADP-ribosylation in transcription catalysed by RNA polymerase I.
mesh_terms: D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D002478:Cells, Cultured; D006224:Cricetinae; D012321:DNA-Directed RNA Polymerases / Q000037:antagonists & inhibitors*; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology; D007668:Kidney / Q000201:enzymology; D009243:NAD / Q000494:pharmacology*; D009244:NAD+ Nucleosidase / Q000378:metabolism*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D012318:RNA Polymerase I / Q000037:antagonists & inhibitors*; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D001549:Benzamides; D009243:NAD; C025160:3-aminobenzamide; D011065:Poly(ADP-ribose) Polymerases; D012321:DNA-Directed RNA Polymerases; D012318:RNA Polymerase I; D009244:NAD+ Nucleosidase