J. Gen. Appl. Microbiol., 51, 245–256 (2005)

Human immunodeficiency virus type-1 (HIV-1), a member of the lentivirus family, encodes two regulatory genes (tat, rev) and four accessory genes (vif, vpr, vpu, nef) in addition to three common retroviral structural genes (gag, pol, env). Viral protein R (Vpr) is a small 14-kDa protein of 96 amino acids. Vpr is incorporated into the virions through its interaction with the p6 region of HIV-1 Gag precursor (Cohen et al., 1990; Paxton et al., 1993; Yuan et al., 1990) and plays a role in the transportation of the viral preintegration complex (PIC) into the nucleus (Heinzinger et al., 1994). Vpr is nonessential for viral replication in T cell lines and activated peripheral blood lymphocytes in vitro but it is necessary for efficient infection of nondividing cells such as macrophages (Balliet et al., 1994; Balotta et al., 1993; Connor et al., 1995; Hattori et al., 1990; Heinzinger et al., 1994; Ogawa et al., 1989; Westervelt et al., 1992). Vpr is highly conserved among other primate lentiviruses; HIV-1, HIV-2 and the Simian immunodeficiency virus (SIV). In the study of macaques infected with wild-type or Vpr-mutant virus, Vpr appeared to increase both the viral load and the rate at which the animals progressed to AIDS (Lang et al., 1993). In addition, in some of the Vpr-mutant virusinfected animals, viral sequences in which Vpr had reverted to wild-type were isolated, suggesting that the presence of a Vpr open reading frame provided a selective advantage to the virus (Gibbs et al., 1995; Goh et al., 1998). In humans, Vpr variants correlate with Mutational analysis of growth arrest and cellular localization of human immunodeficiency virus type 1 Vpr in the budding yeast, Saccharomyces cerevisiae