In the absence of human immunodeficiency virus type 1 (HIV-1) Vif protein, the host antiviral deaminase apolipoprotein B mRNA-editing enzyme-catalytic polypeptide-like 3G (A3G) restricts the production of infectious HIV-1 by deamination of dC residues in the negative single-stranded DNA produced by reverse transcription. The Vif protein averts the lethal threat of deamination by precluding the packaging of A3G into assembling virions by mediating proteasomal degradation of A3G. In spite of this robust Vif activity, residual A3G molecules that escape degradation and incorporate into newly assembled virions are potentially deleterious to the virus. We hypothesized that virion-associated Vif inhibits A3G enzymatic activity and therefore prevents lethal mutagenesis of the newly synthesized viral DNA. Here, we show that (i) Vif-proficient HIV-1 particles released from H9 cells contain A3G with lower specific activity compared with Δvif-virus-associated A3G, (ii) encapsidated HIV-1 Vif inhibits the deamination activity of recombinant A3G, and (iii) purified HIV-1 Vif protein and the Vif-derived peptide Vif25-39 inhibit A3G activity in vitro at nanomolar concentrations in an uncompetitive manner. Our results manifest the potentiality of Vif to control the deamination threat in virions or in the pre-integration complexes following entry to target cells. Hence, virion-associated Vif could serve as a last line of defense, protecting the virus against A3G antiviral activity.
Bibliographical noteFunding Information:
This work was carried out in the Peter A. Krueger Laboratory with the generous support of Nancy and Lawrence Glick and Pat and Marvin Weiss. We thank Dr. D. Gabuzda for providing the Vif-expressing vector and polyclonal Vif serum and Dr. K. Strebel for providing pcDNA-APO3G and pcDNA-APO3G D128K plasmids. The following reagents were obtained through the AIDS Research and Reference Reagent Program, Division of AIDS, NIAID, NIH: HIV-1 Vif peptides from Division of Acquired Immunodeficiency Syndrome, NIAID, and anti-A3G polyclonal antibodies from Dr. Jaisri Lingappa. This work was supported in part by NIH Grant P01 GM091743 , US–Israel Binational Science Foundation , and the Israel Ministry of Health . We thank Drs. Reuben S. Harris, Asaf Friedler and Akram Alian for constructive and helpful discussion and Mrs. S. Amir for editing the manuscript.
- enzyme kinetics
- innate immunity