Lack of correlation between liver RNA polymerase I and ornithine decarboxylase activities after re-feeding of protein-depleted mice.
When mice fed on a protein-depleted diet are restored to the normal diet (re-feeding), there is a 2-fold increase in liver RNA polymerase I activity. The results obtained with pactamycin; an inhibitor of protein synthesis, suggest the presence of short-lived proteins which are required for inducing an activated state of transcription. To gain an insight on whether ornithine decarboxylase (ODC)--the first enzyme in polyamine biosynthesis--is the labile protein that regulates rRNA synthesis, we have investigated the correlation between liver ODC and RNA polymerase I activities under different nutritional conditions. We have also studied the effects of alpha-difluormethylornithine (alpha-DFMO)--a specific ODC inactivator--on rRNA transcription. The results indicate that, after re-feeding, there is an abrupt increase in ODC activity that rapidly declines, while RNA polymerase I is still increasing. On the other hand, alpha-DFMO--which inhibits the elevated activity of ODC--has not effect on rRNA transcription.
D000818:Animals; D004032:Diet; D000518:Eflornithine; D008099:Liver / Q000201:enzymology*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009952:Ornithine / Q000031:analogs & derivatives / Q000378:metabolism; D009955:Ornithine Decarboxylase / Q000378:metabolism*; D065108:Ornithine Decarboxylase Inhibitors; D011488:Protein Deficiency / Q000378:metabolism; D012318:RNA Polymerase I / Q000378:metabolism*
D065108:Ornithine Decarboxylase Inhibitors; D009952:Ornithine; D012318:RNA Polymerase I; D009955:Ornithine Decarboxylase; D000518:Eflornithine