[Double-helical structures in the make up of poly(A)-containing RNA of rat liver cells. Effect of cortisone].

Cytoplasmic poly(A)-containing RNA from rat liver cells are shown to contain RNase-resistant double-stranded regions. Their content increases after cortisone injection. The isolated double-stranded (ds) regions in polyacrylamide gel electrophoresis are seen as discrete bands of three size classes. Their melting curves are typical for double-stranded nucleic acids. The ds-structure isolated from poly(A)+-RNA of cortisone-stimulated rat livers has higher thermostability, with that of control livers. After denaturation 90% of ds-regions become single-stranded. About 50% of denatured double-stranded fragments reassociate at the range of COT = 10(-3)-10(-2). The origin of ds-structures in cytoplasmic poly(A)+-RNA and their possible functions are discussed.