title: Identification of dominant negative human immunodeficiency virus type 1 Vif mutants that interfere with the functional inactivation of APOBEC3G by virus-encoded Vif.
abstract: APOBEC3G (A3G) is a host cytidine deaminase that serves as a potent intrinsic inhibitor of retroviral replication. A3G is packaged into human immunodeficiency virus type 1 virions and deaminates deoxycytidine to deoxyuridine on nascent minus-strand retroviral cDNA, leading to hyper-deoxyguanine-to-deoxyadenine mutations on positive-strand cDNA and inhibition of viral replication. The antiviral activity of A3G is suppressed by Vif, a lentiviral accessory protein that prevents encapsidation of A3G. In this study, we identified dominant negative mutants of Vif that interfered with the ability of wild-type Vif to inhibit the encapsidation and antiviral activity of A3G. These mutants were nonfunctional due to mutations in the highly conserved HCCH and/or SOCS box motifs, which are required for assembly of a functional Cul5-E3 ubiquitin ligase complex. Similarly, mutation or deletion of a PPLP motif, which was previously reported to be important for Vif dimerization, induced a dominant negative phenotype. Expression of dominant negative Vif counteracted the Vif-induced reduction of intracellular A3G levels, presumably by preventing Vif-induced A3G degradation. Consequently, dominant negative Vif interfered with wild-type Vif's ability to exclude A3G from viral particles and reduced viral infectivity despite the presence of wild-type Vif. The identification of dominant negative mutants of Vif presents exciting possibilities for the design of novel antiviral strategies.
authors.affiliation: Laboratory of Microbiology, Viral Biochemistry Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892-0460, USA.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Walker
authors.forename: Mohammad A
authors.initials: MA
authors.lastname: Khan
authors.forename: Sandra
authors.initials: S
authors.lastname: Kao
authors.forename: Ritu
authors.initials: R
authors.lastname: Goila-Gaur
authors.forename: Eri
authors.initials: E
authors.lastname: Miyagi
authors.forename: Klaus
authors.initials: K
authors.lastname: Strebel
mesh_terms: D000071480:APOBEC-3G Deaminase; D002460:Cell Line; D003564:Cytidine Deaminase / Q000037:antagonists & inhibitors*; D015497:HIV-1 / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity*; D006801:Humans; D050296:Microbial Viability; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*; D054320:vif Gene Products, Human Immunodeficiency Virus / Q000235:genetics / Q000378:metabolism*
chemical_list: D050505:Mutant Proteins; D037521:Virulence Factors; D054320:vif Gene Products, Human Immunodeficiency Virus; C514847:vif protein, Human immunodeficiency virus 1; D000071480:APOBEC-3G Deaminase; C464924:APOBEC3G protein, human; D003564:Cytidine Deaminase