title: The Vif and Gag proteins of human immunodeficiency virus type 1 colocalize in infected human T cells.
abstract: The Vif protein of human immunodeficiency virus type 1 (HIV-1) and other lentiviruses is required for efficient replication in primary cells and certain immortalized cell lines in vitro and, in all likelihood, for the establishment of pathogenic infections in vivo. Current hypotheses concerning Vif's mechanism of action posit that it operates in virus-expressing cells during virion assembly, budding, or maturation such that released virions are modified in a manner that enables them to undergo productive infection in subsequent viral challenges. To gain further insight into the mechanism of action of lentivirus Vif proteins, we have performed a variety of in situ localization and biochemical fractionation studies using cells in which Vif is essential for efficient replication. Double-label immunofluorescence analyses of cells productively infected with HIV-1 or feline immunodeficiency virus revealed dramatic patterns of colocalization between Vif and the virally encoded Gag proteins. Subcellular fractionations of human T cells expressing HIV-1 Vif performed in the absence of any detergent demonstrated that greater than 90% of Vif is associated with cellular membranes. Additional purification using a continuous density gradient indicated that the majority of the membrane-bound Vif copurifies with the plasma membrane. Taken together, these observations suggest that lentivirus Vif and Gag proteins colocalize at the plasma membrane as virion assembly and budding take place. As a result, Vif is able to exert its modulatory effect(s) on these late steps of the virus life cycle.
authors.affiliation: Howard Hughes Medical Institute, University of Pennsylvania School of Medicine, Philadelphia 19104-6148, USA.
authors.forename: J H
authors.initials: JH
authors.lastname: Simon
authors.forename: R A
authors.initials: RA
authors.lastname: Fouchier
authors.forename: T E
authors.initials: TE
authors.lastname: Southerling
authors.forename: C B
authors.initials: CB
authors.lastname: Guerra
authors.forename: C K
authors.initials: CK
authors.lastname: Grant
authors.forename: M H
authors.initials: MH
authors.lastname: Malim
mesh_terms: D000818:Animals; D002415:Cats; D002462:Cell Membrane / Q000378:metabolism; D015683:Gene Products, gag / Q000378:metabolism*; D016346:Gene Products, vif / Q000378:metabolism*; D015497:HIV-1 / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D016089:Immunodeficiency Virus, Feline / Q000502:physiology; D051379:Mice; D009584:Nitrogen; D011498:Protein Precursors / Q000378:metabolism*; D011817:Rabbits; D013601:T-Lymphocytes / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured; D054320:vif Gene Products, Human Immunodeficiency Virus
chemical_list: D015683:Gene Products, gag; D016346:Gene Products, vif; D011498:Protein Precursors; C059767:p55 gag precursor protein, Human immunodeficiency virus 1; D054320:vif Gene Products, Human Immunodeficiency Virus; D009584:Nitrogen