title: Nuclear import and cell cycle arrest functions of the HIV-1 Vpr protein are encoded by two separate genes in HIV-2/SIV(SM).
abstract: The vpr genes of human and simian immunodeficiency viruses (HIV/SIV) encode proteins which are packaged in the virus particle. HIV-1 Vpr has been shown to mediate the nuclear import of viral reverse transcription complexes in non-dividing target cells (e.g. terminally differentiated macrophages), and to alter the cell cycle and proliferation status of the infected host cell. Members of the HIV-2/SIV(SM) group encode, in addition to Vpr, a related protein called Vpx. Because these two proteins share considerable sequence similarity, it has been assumed that they also exhibit similar functions. Here, we report that the functions of Vpr and Vpx are distinct and non-redundant, although both proteins are components of the HIV-2/SIV(SM) virion and reverse transcription complex. Characterizing SIV(SM) proviruses defective in one or both genes, we found that Vpx is both necessary and sufficient for the nuclear import of the viral reverse transcription complex. In contrast, Vpr, but not Vpx, inhibited the progression of infected host cells from the G2 to the M phase of the cell cycle. Thus, two independent functions of the HIV-1 Vpr protein are encoded by separate genes in HIV-2/SIV(SM). This segregation is consistent with the conservation of these genes in HIV-2/SIV(SM) evolution, and underscores the importance of both nuclear transport and cell cycle arrest functions in primate lentivirus biology.
authors.affiliation: Department of Medicine, University of Alabama, Birmingham 35294, USA.
authors.forename: T M
authors.initials: TM
authors.lastname: Fletcher
authors.forename: B
authors.initials: B
authors.lastname: Brichacek
authors.forename: N
authors.initials: N
authors.lastname: Sharova
authors.forename: M A
authors.initials: MA
authors.lastname: Newman
authors.forename: G
authors.initials: G
authors.lastname: Stivahtis
authors.forename: P M
authors.initials: PM
authors.lastname: Sharp
authors.forename: M
authors.initials: M
authors.lastname: Emerman
authors.forename: B H
authors.initials: BH
authors.lastname: Hahn
authors.forename: M
authors.initials: M
authors.lastname: Stevenson
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002453:Cell Cycle / Q000235:genetics; D002455:Cell Division / Q000187:drug effects; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D004279:DNA, Viral / Q000378:metabolism; D015683:Gene Products, gag / Q000378:metabolism; D016336:Gene Products, vpr / Q000378:metabolism* / Q000494:pharmacology; D005814:Genes, Viral / Q000235:genetics*; D015498:HIV-2 / Q000235:genetics / Q000378:metabolism*; D000882:Haplorhini; D008264:Macrophages / Q000378:metabolism / Q000821:virology; D016297:Mutagenesis, Site-Directed / Q000235:genetics; D012194:RNA-Directed DNA Polymerase / Q000378:metabolism; D054334:Viral Regulatory and Accessory Proteins / Q000378:metabolism / Q000494:pharmacology; D054325:vpr Gene Products, Human Immunodeficiency Virus
chemical_list: D004279:DNA, Viral; D015683:Gene Products, gag; D016336:Gene Products, vpr; C074286:VPX protein, Human immunodeficiency virus 2; D054334:Viral Regulatory and Accessory Proteins; D054325:vpr Gene Products, Human Immunodeficiency Virus; D012194:RNA-Directed DNA Polymerase