Stepwise dissociation of high molecular weight avian myeloblastosis virus RNA: 30-40S RNA subunits--the best natural template-primer for viral reverse transcriptase.

Controlled disruption of 60S AMV RNA with formamide was used to prepare 50-55S and 30-40S RNAS. When the activities of these RNAs as templates for AMV reverse transcriptase were compared it was found that 50-55S RNA was 1-5 times and 30-40S RNA 2 to 3 times more active than 60S RNA. The 30-40S RNA produced by heating, instead of formamide disruption, was inactive as a template but activity was restored by addition of oligo(dT). 40% of the 4S RNA initially associated with the 60S RNA remained associated with all the RNA species obtained by formamide treatment but was lost on heating. It is concluded that this RNA acts as resident primer whereas the other 60% of the 4S RNA is less firmly bound and appears to have little or no primer activity. Removal of the less firmly bound 4S RNA increases the template activity of the viral RNA.