Effect of a protein-free diet and fasting on RNA polymerase activity in mice.

The objective of this study was to measure the effect of diet on the distribution of RNA polymerase activity in mice kidney. Bound RNA polymerase activity was decreased in kidneys of fasted mice. During a short fast (16 hours), this decrease in bound RNA polymerase I activity was accompanied by an increase in free activity and suggested a possible interference in binding as the reason for decreased bound activity. Bound RNA polymerase II also decreased but with no increase in free activity. During longer fast times (40 hours), the bound RNA polymerase activity (RNA polymerase I and II) remain depressed and the free activity returns to control levels. Fasting decreased bound RNA polymerase I in liver by 41% after 40 hours but had little effect on the free activity. Liver of mice, fed a protein-free diet, were found to have an increased RNA polymerase activity due to a large increase in free RNA polymerase I activity. All other liver RNA polymerase activities were unchanged. In contrast, kidney's of mice fed a protein-free diet, have decreased RNA polymerase activity due to a decrease both in bound RNA polymerase I and II; free RNA polymerase is unchanged. These results demonstrate that diet has a very selective effect on RNA polymerase activity.