HIV-1 Vpr counteracts HLTF-mediated restriction of HIV-1 infection in T cells.

Lentiviruses, including HIV-1, possess the ability to enter the nucleus through nuclear pore complexes and can infect interphase cells, including those actively replicating chromosomal DNA. Viral accessory proteins hijack host cell E3 enzymes to antagonize intrinsic defenses, and thereby provide a more permissive environment for virus replication. The HIV-1 Vpr accessory protein reprograms CRL4 E3 to antagonize select postreplication DNA repair enzymes and activates the DNA damage checkpoint in the G2 cell cycle phase. However, little is known about the roles played by these Vpr targets in HIV-1 replication. Here, using a sensitive pairwise replication competition assay, we show that Vpr endows HIV-1 with a strong replication advantage in activated primary CD4 T cells and established T cell lines. This effect is disabled by a Vpr mutation that abolishes binding to CRL4 E3, thereby disrupting Vpr antagonism of helicase-like transcription factor (HLTF) DNA helicase and other DNA repair pathway targets, and by another mutation that prevents induction of the G2 DNA damage checkpoint. Consistent with these findings, we also show that HLTF restricts HIV-1 replication, and that this restriction is antagonized by HIV-1 Vpr. Furthermore, our data imply that HIV-1 Vpr uses additional, yet to be identified mechanisms to facilitate HIV-1 replication in T cells. Overall, we demonstrate that multiple aspects of the cellular DNA repair machinery restrict HIV-1 replication in dividing T cells, the primary target of HIV-1 infection, and describe newly developed approaches to dissect key components.