Mutational Alteration of Human Immunodeficiency Virus Type 1 Vif Allows for Functional Interaction with Nonhuman Primate APOBEC3G

Infectious Disease Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA.
Journal of Virology (Impact Factor: 4.44). 06/2006; 80(12):5984-91. DOI: 10.1128/JVI.00388-06
Source: PubMed


Human APOBEC3F (hA3F) and APOBEC3G (hA3G) are antiretroviral cytidine deaminases that can be encapsidated during virus assembly to catalyze C-->U deamination of the viral reverse transcripts in the next round of infection. Lentiviruses such as human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) have evolved the accessory protein Vif to induce their degradation before packaging. HIV type 1 (HIV-1) Vif counteracts hA3G but not rhesus macaque APOBEC3G (rhA3G) or African green monkey (AGM) APOBEC3G (agmA3G) because of a failure to bind the nonhuman primate proteins. The species specificity of the interaction is controlled by amino acid 128, which is aspartate in hA3G and lysine in rhA3G. With the objective of overcoming this species restriction, mutations were introduced into HIV-1 Vif at amino acid positions that differed in charge between HIV-1 Vif and SIV Vif. The mutant proteins were tested for the ability to counteract hA3G, rhA3G, and agmA3G. Alteration of the conserved sequence at positions 14 to 17 from DRMR to SERQ, which is the sequence in AGM Vif, caused HIV-1 Vif to functionally interact with rhA3G and agmA3G. Mutation of three residues to the sequence SEMQ allowed interaction with rhA3G. SEMQ Vif also counteracted D128K mutant hA3G and wild-type hA3G. Introduction of the sequence into an infectious molecular HIV-1 clone allowed the virus to replicate productively in human cells that expressed rhA3G or hA3G. These findings provide insight into the interaction of Vif with A3G and are a step toward the development of a novel primate model for AIDS.

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    • "For the first point of contact, we built on the observation that the HIV Vif-resistant mutant A3G-128K is counteracted by a Vif-14- SEMQ-17 mutant (Schrö felbauer et al., 2006). We confirmed this observation by testing the restriction of WT NL4-3, NL4-3 Vif-14- SEMQ-17, and NL4-3 DVif with increasing amounts of WT A3G and the mutant A3G-128K. "
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    ABSTRACT: Human cells express natural antiviral proteins, such as APOBEC3G (A3G), that potently restrict HIV replication. As a counter-defense, HIV encodes the accessory protein Vif, which binds A3G and mediates its proteasomal degradation. Our structural knowledge on how Vif and A3G interact is limited, because a co-structure is not available. We identified specific points of contact between Vif and A3G by using functional assays with full-length A3G, patient-derived Vif variants, and HIV forced evolution. These anchor points were used to model and validate the Vif-A3G interface. The resultant co-structure model shows that the negatively charged β4-α4 A3G loop, which contains primate-specific variation, is the core Vif binding site and forms extensive interactions with a positively charged pocket in HIV Vif. Our data present a functional map of this viral-host interface and open avenues for targeted approaches to block HIV replication by obstructing the Vif-A3G interaction.
    Full-text · Article · Nov 2015 · Cell Reports
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    • "However, due to the incomplete suppression of the tetracycline response element promoter,24 a very small amount of the R88-A3Gm protein was still expressed in the absence of Dox (Figure 1c, lane 1), which could also incorporate into vector particles and impair the vector's transduction efficiency. We thus attempted to promote R88-A3Gm degradation by cotransfecting vector particle–producing cells with the A3GD128K-susceptible HIV-1 VifSEMQ-expressing plasmid.25 Indeed, when VifSEMQ was coexpressed with ProLabel-A3Gm (PL-A3Gm) in 293T cells, the cellular level of the A3Gm protein was reduced by eight times, as measured by ProLabel assay, which is based on the chemiluminescent detection of PL-A3G fusion protein expression (Figure 1d). "
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    • "This region is essential for directing A3G ubiquitination by the E3 ubiquitin ligase complex and corresponds to a nonlinear region located at the N-terminus [32]. Two sequences appear to be important: the first is the 14DRMR17 motif and interacts with APOBEC3F (A3F) sequence (128–130), which is also located at the N-terminus [33], [34]. The other region that plays a functional role is 40YRHHY44 motif; however, this is important only for A3G interaction [35], [36]. "
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    Full-text · Article · Feb 2014 · PLoS ONE
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