Analyses of HIV Integration Components

Abstract

The single-stranded genomic RNA of retroviruses is reverse-transcribed to produce double-stranded linear DNA shortly after entry of the virion into the host cell. For HIV, this reaction has provided the first effective target for anti-viral therapy. Following reverse transcription, viral DNA is stably integrated into the host cell genome. The study of integration is important since this event appears to be obligatory for efficient replication of all retroviruses including HIV and, as with reverse transcription, this reaction has no obvious cellular counterpart. Thus, the integration reaction represents another attractive target for the development of specific inhibitors. Although the requirements for efficient integration of HIV DNA have not yet been thoroughly defined, general features can be inferred from studies with more simple retroviruses, such as the avian sarcoma/leukosis (ASLV) and murine leukemia (MLV) viruses. For these viruses, integration is dependent upon 1) cis-acting sequences at the ends of the linear viral DNA and 2) activities of the integration protein (IN) encoded in the 3′ portion of the retroviral pol gene (Skalka, 1988; Varmus and Brown, 1989; Kulkosky and Skalka, 1990). Recent studies from our laboratory have demonstrated that the ASLV IN is, in fact, both necessary and sufficient to direct integrative recombination in vitro (Katz et al., 1990).