Reduced Transcription Activity of Rat Liver Chromatin after Protein Restriction and Selective Digestion of Nuclei with Micrococcus Nuciease

Abstract

Restriction of protein intake in the diet has been shown to produce a change in transcription activity as determined in vitro. Conditions for a reduced transcription activity were investigated with selective digestion of nuclei with micrococcus nuclease (EC 3.1.4.7). Liver nuclei from young male rats fed a diet containing either 20 or 3% casein for 6 days were digested with 1.3 µg of micrococcus nuclease protein/mg of nuclear DNA (specific enzyme activity 15,000 or 150 units/mg of protein). Part of the chromatin-bound RNA polymerase activity was transferred from the 2,000 × g to the 102,000 × g pellet. Independent of the type of endonuclease used, the specific activity of chromatin-bound and soluble RNA polymerase I plus III was similar in the two groups of rats. After protein restriction RNA polymerase II activity was significantly diminished in the 2,000 × g pellet, and was unchanged in the 102,000 × g pellet. Heparinstimulated and soluble RNA polymerase II activities were significantly reduced. Number and length of RNA chains synthesized by chromatin-bound RNA polymerase I plus III remained unchanged by dietary treatment. After a low protein diet, RNA polymerase II in the absence and presence of heparin synthesized an unchanged number of RNA chains with reduced length. A selective digestion of chromatin with micrococcus nuclease is needed to show the reduction in RNA polymerase II activity after protein restriction.protein restriction RNA polymerase