Characterization of the Low-Molecular-Weight RNAs Associated with the 70 S RNA of Rous Sarcoma Virus

Abstract

Two low-molecular-weight RNAs are associated with the 70 S RNA complex of Rous sarcoma virus: a previously described 4 S RNA and a newly identified 5 S RNA. The 4 S RNA constitutes 3 to 4% of the 70 S RNA complex or the equivalent of 12 to 20 molecules per 70 S RNA. It exhibits a number of structural properties characteristic of transfer RNA as revealed by two-dimensional electrophoresis of oligonucleotides obtained from a T1 ribonuclease digest of the 4 S RNA species. The 5 S RNA is approximately 120 nucleotides in length, constitutes 1% of the 70 S RNA complex or the equivalent of 3 to 4 molecules per molecules of 70 S RNA, and is identical in nucleotide composition and structure to 5 S RNA from uninfected chicken embryo fibroblasts. Melting studies indicate that the 5 S RNA is released from the 70 S RNA complex at the same temperature required to dissociate 70 S RNA into its constituent 35 S subunits. In contrast, greater than 80% of the 4 S RNA is released from 70 S RNA prior to its conversion into subunits. The possible biological significance of these 70 S -associated RNAs is discussed.