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J. Virol., Aug 1997, 5774-5781, Vol 71, No. 8
M Kotler, M Simm, YS Zhao, P Sova, W Chao, SF Ohnona, R Roller, C Krachmarov, MJ Potash and DJ Volsky
Human immunodeficiency virus type 1 (HIV-1) Vif is required for productive
infection of T lymphocytes and macrophages. Virions produced in the absence
of Vif have abnormal core morphology and those produced in primary T cells
carry immature core proteins and low levels of mature capsid (M. Simm, M.
Shahabuddin, W. Chao, J. S. Allan, and D. J. Volsky, J. Virol.
69:4582-4586, 1995). To investigate whether Vif influences the activity of
HIV-1 protease (PR), the viral enzyme which is responsible for processing
Gag and Gag-Pol precursor polyproteins into mature virion components, we
transformed bacteria to inducibly express truncated Gag-Pol fusion proteins
and Vif. We examined the cleavage of polyproteins consisting of matrix to
PR (Gag-PR), capsid to PR (CA-PR), and p6Pol to PR (p6Pol-PR) and evaluated
HIV-1 protein processing at specific sites by Western blotting using
antibodies against matrix, capsid, and PR proteins. We found that Vif
modulates HIV-1 PR activity in bacteria mainly by preventing the release of
mature MA and CA from Gag-PR, CA from CA-PR, and p6Pol from p6Pol-PR, with
other cleavages being less affected. Using subconstructs of Vif, we mapped
this activity to the N-terminal half of the molecule, thus identifying a
new functional domain of Vif. Kinetic study of p6Pol-PR autocatalysis in
the presence or absence of Vif revealed that Vif and N'Vif reduce the rate
of PR-mediated proteolysis of this substrate. In an assay of in vitro
proteolysis of a synthetic peptide substrate by purified recombinant PR we
found that recombinant Vif and the N- terminal half of the molecule
specifically inhibit PR activity at a molar ratio of the N-terminal half of
Vif to PR of about 1. These results suggest a mechanism and site of action
of Vif in HIV-1 replication and demonstrate novel regulation of a
lentivirus PR by an autologous viral protein acting in trans.
Copyright © 1997, American Society for Microbiology
Human immunodeficiency virus type 1 (HIV-1) protein Vif inhibits the activity of HIV-1 protease in bacteria and in vitro
Department of Molecular Genetics, Hadassah Medical School, Hebrew University, Jerusalem, Israel.
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