Control of activation of liver RNA polymerase I occurring after re-feeding of protein-depleted mice

• Published in: Biochemical journal Vol. 210; no. 3; pp. 837 - 844
• Main Authors: Haim, L, Iapalucci-Espinoza, S, Conde, R, Franze-Fernández, M T
• Format: Journal Article
• Language: English
• Published: England 15.03.1983
• Subjects: Animals; Cell Nucleus - enzymology; Dietary Proteins - pharmacology; DNA - metabolism; DNA-Directed RNA Polymerases - metabolism; Enzyme Activation - drug effects; Food; Liver - drug effects; Liver - enzymology; Male; Mice; Pactamycin - pharmacology; Protein Deficiency - metabolism; RNA Polymerase I - antagonists & inhibitors; RNA Polymerase I - metabolism
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/bj2100837

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.