Initiation of DNA synthesis by the avian oncornavirus RNA-directed DNA polymerase: Structural and functional localization of the major species of primer RNA on the oncornavirus genome

Abstract

We have both structurally and functionally localized the site on the avian oncornavirus RNA genome at which the major species of primer RNA is bound. Localization of the primer site involved either determining the minimum size class of poly(A)-containing fragments of the viral RNA genome to which radiolabeled primer RNA would anneal, or determining the minimum size class of poly(A)-containing fragments that could be reconstituted as an active template primer complex for the RNA-directed DNA polymerase subsequent to reannealing to unlabeled purified primer RNA. Both approaches indicate that the primer site appears to be very close to (within 10%), or at the 5′ end of the 35 S RNA genome. The implications of these findings on the transcription of the oncornavirus genome in vitro and in vivo are discussed.