Reverse transcriptase as the major determinant for selective packaging of tRNA's into Avian sarcoma virus particles

Abstract

Mutants of avian sarcoma virus which lack a functional DNA polymerase were found to be nonselective in the incorporation of host cell tRNA9s into virus particles. In contrast, mutants which possess a functional DNA polymerase but lack the viral genome RNA contained a specific subset of the host cell tRNA population, indistinguishable from that of the wild-type virus. Thus the reverse transcriptase, and not the viral RNA, is probably the major factor determining which tRNA9s are incorporated into avian sarcoma virus particles. Supporting evidence was obtained in an in vitro binding assay between purified reverse transcriptase and unfractionated cellular tRNA9s. However, the subset of tRNA9s which associated with the genome in the 70S complex was determined primarily by the viral RNA. In the absence of DNA polymerase, the 70S RNA complex in mature virus particles contained the normal complement of associated tRNA9s with the exception of tRNATrp, the primer for RNA-directed DNA synthesis. Images