The low molecular weight RNAs of Rous sarcoma virus: II. The 7 S RNA

Purified preparations of both the Bryan and Schmidt-Ruppin strains of Rous sarcoma virus contain two populations of low molecular weight RNA—a previously described 4 S RNA, which is probably transfer RNA derived from the host cell, and a newly identified 7 S RNA. The latter has been purified by chromatography on columns of methylated albumin kieselguhr, and has been found to be a single-stranded molecule with a molecular weight of approximately 80,000. It constitutes 3–5% of the total viral RNA, or 5–10 molecules per virion. The nucleotide composition of 7 S RNA is different for each strain of virus. The 7 S RNA is not detectably methylated, and thus is probably not a special form of transfer RNA. It has not been possible to identify a corresponding form of RNA in either normal or infected cells. Annealing experiments indicate that neither the 4 S nor the 7 S viral RNA is complementary to the RSV genome. The origin and significance of RSV 7 S RNA is presently indeterminate.