Effects of inhibitors of energetic metabolism on RNA turnover in animal cells

Abstract

The turnover of RNA in ascites tumor cells of rat ovaries was studied in the presence of the following inhibitors of energetic metabolism: monoiodacetate, fluoride, azide, 2,4-dinitrophenol, cyanide, rotenone, oligomycin and antimycin. The incubation of cells with monoiodacetate (5 · 10 −3 M), fluoride (10 −2 M), 2,4-dinitrophenol (5 · 10 −4 M), oligomycin (10 μg/ml) and antimycin (10 μg/ml) results in a prompt and complete block of precursor incorporation into RNA. Protein synthesis is blocked at the same time. Azide (2 · 10 −3 mM), rotenone (1 · 10 −7 M), oligomycin (0.5 μg/ml) and antimycin (0.5 μg/ml) block RNA synthesis only after a 60-min incubation of the cells with these agents. In the first minutes of incubation, cyanide (5 · 10 −3 M) causes some stimulation of precorsor incorporation, but this changes to full inhibition of RNA synthesis 60 min later. All the energetic metabolism inhibitors have no specificity in the inhibition of RNA synthesis. Sedimentation patterns and base composition of RNA formed in the presence of energetic metabolism inhibitors are not changed. Some specificity in the action of the inhibitors begins to develop only under conditions of very strong (about 90 %) inhibition of overall RNA synthesis, when the synthesis of G · C-type RNA is preferently blocked. Actinomycin D, studied for comparison, inhibits the synthesis of G · C-type RNA under conditions of as little as 10–20 % block. The partial decay of rapidly labelled RNA which can be found in cells after chase with actinomycin D is completely suppressed when the chase is induced in the presence of energetic metabolism inhibitors. The base composition and sedimentation coefficients of labelled RNA remain unchanged when decay is delayed. Thus, the energetic metabolism inhibitors suppress the processing of newly formed RNA. This delay of RNA processing is not connected with the direct influence of energetic metabolism inhibitors on the hydrolytic enzymes involved in RNA metabolism. The data obtained show that the processes of RNA turnover in animal cells depend on the integrity of energetic mechanisms.