title: Identification of a tripartite interaction between the N-terminus of HIV-1 Vif and CBFβ that is critical for Vif function.
abstract: HIV-1 Vif interacts with the cellular core-binding factor β (CBFβ) and counteracts the protective roles of certain human APOBEC3 (A3) proteins by targeting them for proteasomal degradation. Previous studies have identified some amino acids important for Vif-CBFβ interactions, and recently a co-crystal structure of a pentameric complex of HIV-1 Vif, CBFβ, Cul5, EloB, and EloC was resolved. However, a comprehensive analysis of Vif-CBFβ interactions that are important for Vif function has not been performed.
  
  
  
  Here, we carried out double-alanine scanning mutagenesis of the first 60 amino acids of Vif and determined their effects on interaction with CBFβ and their ability to induce A3G degradation as well as rescue HIV-1 replication in the presence of A3G. We found that multiple Vif residues are involved in the extensive N-terminal Vif-CBFβ interaction and that the5WQVMIVW11region of Vif is the major determinant. A minimum of three alanine substitutions are required to completely abrogate the Vif-CBFβ interaction and Vif's ability to rescue HIV-1 infectivity in the presence of A3G. Mutational analysis of CBFβ revealed that F68 and I55 residues are important and participate in a tripartite hydrophobic interaction with W5 of Vif to maintain a stable and functional Vif-CBFβ complex. We also determined that CBFβ amino acids73WQGEQR78, which are not resolved in the structure of the pentameric complex, are not involved in interaction with HIV-1 Vif.
  
  
  
  Our results provide detailed insight into the Vif-CBFβ interactions that are critical for Vif function and may contribute to the rational design of HIV-1 inhibitors that block Vif-mediated degradation of A3 proteins.
authors.affiliation: Viral Mutation Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702, USA.
authors.forename: Belete A
authors.initials: BA
authors.lastname: Desimmie
authors.affiliation: Viral Mutation Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702, USA.
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Smith
authors.affiliation: Basic Research Laboratory, Leidos Biomedical Research, Inc., Frederick National Laboratory, Frederick, MD, USA.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Matsuo
authors.affiliation: Viral Recombination Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD, USA.
authors.forename: Wei-Shau
authors.initials: WS
authors.lastname: Hu
authors.affiliation: Viral Mutation Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702, USA. vinay.pathak@nih.gov.
authors.forename: Vinay K
authors.identifier: 0000-0003-2441-8412
authors.initials: VK
authors.lastname: Pathak
mesh_terms: D019943:Amino Acid Substitution; D050658:Core Binding Factor beta Subunit / Q000235:genetics / Q000378:metabolism*; D004252:DNA Mutational Analysis; D015497:HIV-1 / Q000502:physiology*; D054884:Host-Pathogen Interactions; D006801:Humans; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D025941:Protein Interaction Mapping; D054320:vif Gene Products, Human Immunodeficiency Virus / Q000235:genetics / Q000378:metabolism*
chemical_list: C493692:CBFB protein, human; D050658:Core Binding Factor beta Subunit; D054320:vif Gene Products, Human Immunodeficiency Virus; C514847:vif protein, Human immunodeficiency virus 1
keywords: APOBEC3G; CBFβ; HIV-1; Proteasomal degradation; Restriction factor; Vif