The Effect of Radiation on Processing of Nuclear RNA and Chromatin Ribonuclease Activity in Rat Liver and Thymus

Summary

The effect of radiation on the kinetics of nuclear RNA degradation was studied during actinomycin chase. The intranuclear breakdown of RNA in thymus was inhibited for the first 30–120 min after 800 R irradiation of rats. In liver the degradation of nuclear RNA was unchanged for 60 min after irradiation. By the second hour, the breakdown of the rRNA precursor accelerated and the processing of D-RNA slowed down. Rat thymus and liver chromatin showed RNAase activity with two optimal pH values–in the acidic (pH 5·0–5·5) and weakly alkaline (pH 7·5) regions. The activity of the acidic RNAase of thymus (but not the liver) chromatin fell after 5–20 kR irradiation in vitro. The activity of the alkaline RNAase did not change under these conditions. The data indicate that a fall in activity of the acidic RNAase in irradiated thymus chromatin may be related to disturbance in the enzyme-inhibitor interaction. A possible contribution of the chromatin acidic RNAase to the processing of nuclear RNA in control and after irradiation is discussed.