Aström S, Arrhenius E K, von der Decken A
J Nutr. 1981 Jul;111(7):1258-64. doi: 10.1093/jn/111.7.1258.
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 microgram 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 use, 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. Heparin-stimulated and soluble RNA polymerase II activities were significantly reduced. Number and length of RNA chains synthetized 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.
饮食中蛋白质摄入量的限制已被证明会在体外测定时引起转录活性的变化。用微球菌核酸酶（EC 3.1.4.7）选择性消化细胞核，研究了转录活性降低的条件。将喂食含20%或3%酪蛋白饮食6天的年轻雄性大鼠的肝细胞核，用1.3微克微球菌核酸酶蛋白/毫克核DNA（比酶活性15,000或150单位/毫克蛋白）进行消化。部分与染色质结合的RNA聚合酶活性从2000×g沉淀物转移到102000×g沉淀物中。无论使用何种类型的内切酶，两组大鼠中与染色质结合的和可溶性的RNA聚合酶I加III的比活性相似。蛋白质限制后，2000×g沉淀物中的RNA聚合酶II活性显著降低，而102000×g沉淀物中的活性不变。肝素刺激的和可溶性的RNA聚合酶II活性显著降低。饮食处理后，与染色质结合的RNA聚合酶I加III合成的RNA链的数量和长度保持不变。低蛋白饮食后，在不存在和存在肝素的情况下，RNA聚合酶II合成的RNA链数量不变，但长度缩短。需要用微球菌核酸酶对染色质进行选择性消化，以显示蛋白质限制后RNA聚合酶II活性的降低。
