Reassociation of 4 S and 5 S RNA's with the genome of avian sarcoma virus

Abstract

A tryptophan tRNA derived from the host cell serves as primer for the initiation of DNA synthesis by the reverse transcript ase of avian sarcoma virus (ASV). We have characterized the binding of primer to the viral genome by studying the reassociation of low molecular weight RNA's with high molecular weight subunits of ASV-RNA. Primer can be annealed to a limited number (two to four) of sites on the viral genome to reconstitute a template fully active with reverse transcriptase. The annealing is specific and accurate; none of the other 4 S RNA's found in ASV will reassociate with viral genome under any of the conditions tested, and the reconstructed complex denatures with the same T m as the native complex between primer and viral genome. These results further substantiate our previous conclusion that the primer in ASV is a single species of tRNA, although the normal host cell may contain other 4 S RNA's which could also serve as primer if they were included in the viral genome during assembly. Chicken ribosomal 5 S RNA also reanneals to the ASV genome, presumably by binding to the sites originally occupied by 5 S RNA in viral 70 S RNA.