MULTIPLE SITES OF ACTION OF N-HYDROXY-2-ACETYLAMINOFLUORENE IN RAT HEPATIC NUCLEAR TRANSCRIPTION

Abstract

This study attempts to identify the site(s) of action of N-hydroxy-2-acetylaminofluorene (N-OH-AAF) in relation to its inhibition of rat hepatic nuclear RNA synthesis. Two hours after N-OH-AAF injection (3 mg/100 g body wt), rat hepatic nuclear synthesis and nucleolar RNA synthesis in vitro were inhibited by 60 and 80%, respectively. When total nuclear RNA polymerases were solubilized and assayed in the presence of .alpha.-amanitin (3.2 .mu.g/ml), only .alpha.-amanitin-sensitive activity was reduced (50%) by N-OH-AFF. DEAE Sephadex column chromatography confirmed this finding and further demonstrated that RNA polymerase II was the activity selectively inhibited. Since N-OH-AFF dramatically inhibited nucleolar RNA synthesis but had little effect on RNA polymerase I activity, in addition to its direct inhibitory effect on the enzyme function of RNA polymerase II, N-OH-AFF must also cause impairment of nucleolar DNA template function.