title: Control of activation of liver RNA polymerase I occurring after re-feeding of protein-depleted mice.
abstract: Shortly after feeding protein-depleted mice with a meal containing protein, the RNA polymerase I activity in isolated liver nuclei shows a 2-fold increase over the values in the nuclei of either normal or protein-depleted mice. The activity of the RNA polymerase I solubilized from nuclei of re-fed mice was slightly enhanced, probably reflecting an increase in enzyme amount. However, this increase only accounts for about 30% of the stimulation of transcription in the intact nuclei. Administration of pactamycin, an inhibitor of protein synthesis, to normal or protein-depleted mice has almost no inhibitory effect on the RNA polymerase I activity in the isolated nuclei. On the contrary, within 15 min after treatment with the drug, the stimulated activity in nuclei from re-fed mice declines towards the values in normal or protein-depleted mice and then remains constant. The activity of the solubilized enzyme remains slightly elevated for at least 2 1/2 h after re-fed mice are treated with pactamycin. These observations indicate that the stimulation of the RNA polymerase I activity in the intact nuclei after re-feeding is controlled by mechanisms other than an increase in the enzyme amount and suggest the presence of short-lived proteins required for inducing an activated state of transcription.
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology; D004247:DNA / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D004044:Dietary Proteins / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005502:Food; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D051379:Mice; D010142:Pactamycin / Q000494:pharmacology; D011488:Protein Deficiency / Q000378:metabolism*; D012318:RNA Polymerase I / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D004044:Dietary Proteins; D010142:Pactamycin; D004247:DNA; D012321:DNA-Directed RNA Polymerases; D012318:RNA Polymerase I