ABSTRACT
HIV-1 virion infectivity factor (Vif) promotes degradation of the antiviral APOBEC3 (A3) proteins through the host ubiquitin-proteasome pathway to enable viral immune evasion. Disrupting Vif-A3 interactions to reinstate the A3-catalyzed suppression of human immunodeficiency virus type 1 (HIV-1) replication is a potential approach for antiviral therapeutics. However, the molecular mechanisms by which Vif recognizes A3 proteins remain elusive. Here we report a cryo-EM structure of the Vif-targeted C-terminal domain of human A3F in complex with HIV-1 Vif and the cellular cofactor core-binding factor beta (CBFß) at 3.9-Å resolution. The structure shows that Vif and CBFß form a platform to recruit A3F, revealing a direct A3F-recruiting role of CBFß beyond Vif stabilization, and captures multiple independent A3F-Vif interfaces. Together with our biochemical and cellular studies, our structural findings establish the molecular determinants that are critical for Vif-mediated neutralization of A3F and provide a comprehensive framework of how HIV-1 Vif hijacks the host protein degradation machinery to counteract viral restriction by A3F.
Subject(s)
Cytosine Deaminase/chemistry , HIV-1/chemistry , vif Gene Products, Human Immunodeficiency Virus/chemistry , Core Binding Factor beta Subunit/chemistry , Cryoelectron Microscopy , Cytosine Deaminase/antagonists & inhibitors , Cytosine Deaminase/ultrastructure , Humans , Immune Evasion , Models, Molecular , Protein Conformation , Protein Domains , Protein Interaction Mapping , Proteolysis , Structure-Activity Relationship , vif Gene Products, Human Immunodeficiency Virus/pharmacology , vif Gene Products, Human Immunodeficiency Virus/ultrastructureABSTRACT
Herpes simplex virus type-1 thymidine kinase (HSV-1TK) and Escherichia coli cytosine deaminase (CD) fusion protein was designed using InsightII software. The structural rationality of the fusion proteins incorporating a series of flexible linker peptide was analyzed, and a suitable linker peptide was chosen for further investigated. The recombinant plasmid containing the coding regions of HSV-1TK and CD cDNA connected by this linker peptide coding sequence was generated and subsequently transfected into the human embryonic kidney 293 cells (HEK293). The Western blotting indicated that the recombinant fusion protein existed as a dimer with a molecular weight of approximately 90 kDa. The toxicity of the prodrug on the recombinant plasmid-transfected human lung cancer cell line NCIH460 was evaluated, which showed that TKglyCD-expressing cells conferred upon cells prodrug sensitivities equivalent to that observed for each enzyme independently. Most noteworthy, cytotoxicity could be enhanced by concurrently treating TKglyCD-expressing cells with prodrugs GCV and 5-FC. The results indicate that we have successfully constructed a HSV-1TKglyCD fusion gene which might have a potential application for cancer gene therapy.
