This research plan proposes to contribute to the understanding of the subunit structure and function of oncornavirus RNAs. First, an attempt will be made to separate and characterize in as much detail as possible the putative RNA subunits of a model oncornavirus, Rous sarcoma virus, using differences in bouyant density, gel electrophoresic mobility, chromatographic behavior, poly (A) content and selective dissociation from the 70S genome RNA complex as possible means for effecting this separation. Binding of ethidium bromide and deoxyribo polymers will be combined with some of the above separation procedures in order to exploit possible differences in RNA subunit secondary structure and base composition. Second, the linkage between RNA subunits will be investigated by attempting to covalently crosslink with 4,5'-,8-trimethyl psoralen the presumed base-paired regions involved in the linkages. This crosslinked structure would then be digested with ribonuclease at high salt concentrations in order to determine the sizes, number, and sequences involved in base-paired regions.