Nuclear and mitochondrial origin of rat liver double-stranded RNA

We have studied the intracellular location of double-stranded RNA from rat liver. The majority of this dsRNA is associated with nuclear and mitochondrial fractions and the remaining portion is associated with microsomes. Mitochondrial dsRNA hybridizes specifically with purified strands of mitochondrial DNA and seems therefore to arise from transcription of the latter. A fraction of nuclear dsRNA hybridizes with repetitive sequences of nuclear DNA. Because of self-hybridization of dsRNA strands, it was not possible to determine whether another fraction of DSRNA is homologous to nonrepetitive sequences of DNA. Both mitochondrial and nuclear types of dsRNA are not retained on oligo(dT) cellulose columns and therefore seem to lack long poly A sequences. The mechanism of formation of dsRNA is discussed.