Role of Vif in human immunodeficiency virus type 1 reverse transcription

Abstract

The Vif protein of human immunodeficiency virus type 1 (HIV-1) is important for virion infectivity. Previous studies have shown that vif mutant HIV-1 virions are defective in their ability to synthesize proviral DNA in vivo. Here, we examine the role of Vif in viral DNA synthesis in the endogenous reverse transcriptase (RT) reaction, an in vitro assay in which virions synthesize viral DNA by using endogenous viral RNA as a template. vif mutant virions showed a significant reduction in endogenous RT activity despite similar levels of exogenous RT activity. Analysis of the viral DNA products on agarose gels demonstrated that this reflects reduced synthesis of short minus-and plus-strand DNA products in addition to those of full genomic length. Quantitative PCR analysis of endogenous reverse transcription provided further evidence for reduced formation of both initial and completed reverse transcripts. Vif had no effect on genomic RNA dimerization or the stability of the RNA dimer linkage. These results suggest that Vif is important for an early event after virus entry but preceding or during the early stages of viral DNA synthesis. This may be due to an intrinsic effect on reverse transcription or a preceding postentry event(s), such as virion uncoating or disassembly of the virion core. Drugs targeted to Vif function may provide a new therapeutic approach to inhibiting HIV-1 reverse transcription.

The regulation of primate immunodeficiency virus infectivity by Vif is cell species restricted: a role for Vif in determining virus host range and cross-species transmission

“…Virus particles expressed in the absence of a functional Vif protein are able to bind to and penetrate susceptible cells but are severely debilitated in their capacity to establish proviruses (Sova and Volsky, 1993; von Schwedler et al ., 1993; Simon and Malim, 1996). Consistent with this, it has been proposed that the defect in vif ‐deficient infections may be manifested as the post‐entry instability of viral nucleoprotein complexes (Goncalves et al ., 1996; Simon and Malim, 1996). Significantly, challenges with vif ‐deficient viruses cannot be rescued back to productivity by the presence of Vif in the target cells (Gabuzda et al ., 1992; von Schwedler et al ., 1993).…”

“…The critical contribution of the Vif family of proteins to virus infectivity and replication has been established for a variety of primate and non‐primate lentiviruses. Although the precise mechanism by which Vif regulates infectivity remains to be defined, the prevailing view is that late steps of the virus life cycle (assembly, maturation and/or budding) are manipulated such that ensuing virions are able to complete reverse transcription and establish proviruses following penetration into susceptible cells (Gabuzda et al ., 1992; Sova and Volsky, 1993; von Schwedler et al ., 1993; Goncalves et al ., 1996; Simon and Malim, 1996). In an endeavor to understand Vif function in greater detail, we have been investigating the patterns of cross‐complementation between the Vif proteins of divergent lentiviruses.…”

Blockade of HIV-1 Infection of New World Monkey Cells Occurs Primarily at the Stage of Virus Entry

“…The early, post-entry block to HIV-1 infection seen in Old World monkeys does not appear to be operative in New World monkeys. Cellular cofactors in New World monkey cells must be able to interact functionally with the HIV-1 Tat, Rev, and Vif proteins to allow successful completion of the late phase of virus replication (71)(72)(73)(74). Likewise, New World monkey HP68 and cyclophilin A are apparently compatible with HIV-1 Gag components to allow capsid formation and the attainment of virion infectivity, respectively (75)(76)(77)(78).…”

A second human antiretroviral factor, APOBEC3F, is suppressed by the HIV-1 and HIV-2 Vif proteins

“…Cell lysates, virion lysates and immunoprecipitates were subjected to gel electrophoresis and then transferred to a nitrocellulose membrane. The membranes were probed with a mouse monoclonal antibody specific for the HIV-1 capsid protein (Chesebro et al, 1992) or rabbit polyclonal antisera specific for the HA epitope tag (Covance), HIV-1 Vif (Goncalves et al, 1996) or the N-peptide tag (Wiegand et al, 2003). Reactive proteins were detected using the Lumi-Light Western Blotting Substrate (Roche), as previously described (Bogerd et al, 2004).…”