The low molecular weight RNAs of Rous sarcoma virus: I. The 4 S RNA

Chromatography of Rous sarcoma virus RNA on methylated albumin-kieselguhr has allowed the identification of four classes of intravirion RNA: a substantial amount of 4 S RNA, a discrete 7 S component, small quantities of 18 and 28 S RNA, and the 70 S RNA of the viral genome. The 4 S RNA's of the virus and its host cell have identical electrophoretic mobilities in 10% polyacrylamide gels and are methylated to the same extent. However, significant differences in nucleotide compositions are detectable. The virus apparently does not contain RNA corresponding to any of the other low molecular weight species of cellular RNA. The data are in accord with previous suggestions that RNA tumor viruses contain tRNA acquired from the host cell during assembly, but also indicate at least minor differences in composition between the cellular and viral 4 S RNA populations. The results of reconstruction experiments suggest that the viral 4 S RNA is not simply a contaminant derived from cellular debris.