Roles of Pr55 gag and NCp7 in tRNA 3 Lys Genomic Placement and the Initiation Step of Reverse Transcription in Human Immunodeficiency Virus Type 1

Abstract

ABSTRACT To study in vivo tRNA 3 Lys genomic placement and the initiation step of reverse transcription in human immunodeficiency virus type 1, total viral RNA isolated from either wild-type or protease-negative (PR − ) virus was used as the source of primer tRNA 3 Lys /genomic RNA templates in an in vitro reverse transcription assay. At low dCTP concentrations, both the rate and extent of the first nucleotide incorporated into tRNA 3 Lys , dCTP, were lower with PR − than with wild-type total viral RNA. Transient in vitro exposure of either type of primer/template RNA to NCp7 increased PR − dCTP incorporation to wild-type levels but did not change the level of wild-type dCTP incorporation. Exposure of either primer/template to Pr55 gag had no effect on initiation. These results indicate that while Pr55 gag is sufficient for tRNA 3 Lys placement onto the genome, exposure of this complex to mature NCp7 is required for optimum tRNA 3 Lys placement and initiation of reverse transcription.