Intravirion processing of the human immunodeficiency virus type 1 Vif protein by the viral protease may be correlated with Vif function.
The human immunodeficiency virus type 1 (HIV-1) Vif protein is specifically packaged into virus particles through an interaction with viral genomic RNA in which it associates with the viral nucleoprotein complex. We now demonstrate for the first time that virus-associated Vif is subject to proteolytic processing by the viral protease (Pr). Pr-dependent processing of Vif was observed both in vivo and in vitro. In vivo processing of Vif was cell type independent and evident by the appearance of a 7-kDa processing product, which was restricted to cell-free virus preparations. Processing of Vif required an active viral Pr and was sensitive to Pr inhibitors such as ritonavir. The processing site in Vif was characterized both in vivo and in vitro and mapped to Ala(150). Interestingly, the Vif processing site is located in a domain that is highly conserved among HIV-1, HIV-2, and simian immunodeficiency virus Vif isolates. Mutations at or near the processing site did not affect protein stability or packaging efficiency but had dramatic effects on Vif processing. In general, mutations that markedly increased or decreased the sensitivity of Vif to proteolytic processing severely impaired or completely abolished Vif function. In contrast, mutations at the same site that had little or no effect on processing efficiency also did not influence Vif function. None of the mutants affected the ability of the virus to replicate in permissive cell lines. Our data suggest that mutations in Vif that cause a profound change in the sensitivity to Pr-dependent processing also severely impaired Vif function, suggesting that intravirion processing of Vif is important for the production of infectious viruses.
Laboratory of Molecular Microbiology. Viral Biochemistry Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Mohammad A
MA
Khan
Hirofumi
H
Akari
Sandra
S
Kao
Claudia
C
Aberham
David
D
Davis
Alicia
A
Buckler-White
Klaus
K
Strebel
D000595:Amino Acid Sequence; D002460:Cell Line; D016346:Gene Products, vif / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016333:HIV Protease / Q000378:metabolism*; D015497:HIV-1 / Q000201:enzymology / Q000378:metabolism* / Q000472:pathogenicity; D006367:HeLa Cells; D006801:Humans; D019169:Jurkat Cells; D008969:Molecular Sequence Data; D009154:Mutation; D014771:Virion / Q000378:metabolism*; D014779:Virus Replication; D054320:vif Gene Products, Human Immunodeficiency Virus
D016346:Gene Products, vif; D054320:vif Gene Products, Human Immunodeficiency Virus; D016333:HIV Protease