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The Wenner-Gren Institute for Experimental Biology, S-113 45 Stockholm, Sweden
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 x g to the 102,000 x 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 x g pellet, and was unchanged in the 102,000 x 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.
KEY WORDS: protein restriction RNA polymerase
1 Supported in part by Grant No. 1 ROI CA26642-01, awarded to A.v.d.D. by the National Cancer Institute, DHEW, Washington, DC.
2 Present address: Department of Pharmacological Research, KABI AB, Lindhagensgatan 133, S-112 87 Stockholm, Sweden.
Manuscript received 1 December 1980.
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