THE PUTATIVE ALPHA-HELIX-2 OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 VPRCONTAINS A DETERMINANT WHICH IS RESPONSIBLE FOR THE NUCLEAR TRANSLOCATION OF PROVIRAL DNA IN GROWTH-ARRESTED CELLS

Several viral determinants were shown to play a role in the ability of human immunodeficiency virus type 1 (HIV-1) to infect nondividing cel ls. In particular, Vpr and Gag matrix (MA) were recognized to be invol ved in the nuclear transport of the viral preintegration complex. The goal of the present study was to evaluate the ability of isogenic HIV- 1 viruses harboring different vpr and gag genes to infect nondividing cells. Surprisingly, our results reveal that the introduction of mutat ions in the MA nuclear localization signal marginally affected the abi lity of proviruses to establish infection in growth-arrested HeLa or M T4 cells. In contrast, we show that in our experimental system, the ab sence of Vpr expression leads to a reduction in viral infectivity and production which correlates with a decrease in the synthesis and nucle ar transport of proviral DNA as determined by PCR analysis. Moreover, our data demonstrate that this reduction of viral replication is also observed with proviruses containing different mutated Vpr alleles. In particular, the Vpr Q65E mutant, which contains a substitution in the second predicted amphipathic alpha-helical structure located in the ce ntral region of the protein, is associated with an impairment of the p rotein nuclear localization and a concomitant reduction of the nuclear transport of proviral DNA. The results of this study provide evidence that a putative amphipathic alpha-helical structure in the central re gion of Vpr contains a determinant involved in the nuclear translocati on of the preintegration complex in nondividing cells.