title: Core Binding Factor β Protects HIV, Type 1 Accessory Protein Viral Infectivity Factor from MDM2-mediated Degradation.
abstract: HIV, type 1 overcomes host restriction factor apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like 3 (APOBEC3) proteins by organizing an E3 ubiquitin ligase complex together with viral infectivity factor (Vif) and a host transcription cofactor core binding factor β (CBFβ). CBFβ is essential for Vif to counteract APOBEC3 by enabling the recruitment of cullin 5 to the complex and increasing the steady-state level of Vif protein; however, the mechanisms by which CBFβ up-regulates Vif protein remains unclear. Because we have reported previously that mouse double minute 2 homolog (MDM2) is an E3 ligase for Vif, we hypothesized that CBFβ might protect Vif from MDM2-mediated degradation. Co-immunoprecipitation analyses showed that Vif mutants that do not bind to CBFβ preferentially interact with MDM2 and that overexpression of CBFβ disrupts the interaction between MDM2 and Vif. Knockdown of CBFβ reduced the steady-state level of Vif in MDM2-proficient cells but not in MDM2-null cells. Cycloheximide chase analyses revealed that Vif E88A/W89A, which does not interact with CBFβ, degraded faster than wild-type Vif in MDM2-proficient cells but not in MDM2-null cells, suggesting that Vif stabilization by CBFβ is mainly caused by impairing MDM2-mediated degradation. We identified Vif R93E as a Vif variant that does not bind to MDM2, and the virus with this substitution mutation was more resistant to APOBEC3G than the parental virus. Combinatory substitution of Vif residues required for CBFβ binding and MDM2 binding showed full recovery of Vif steady-state levels, supporting our hypothesis. Our data provide new insights into the mechanism of Vif augmentation by CBFβ.
authors.affiliation: From the Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Matsui
authors.affiliation: From the Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan shind009@kuhp.kyoto-u.ac.jp.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Shindo
authors.affiliation: From the Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan.
authors.forename: Kayoko
authors.initials: K
authors.lastname: Nagata
authors.affiliation: From the Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan.
authors.forename: Noriyoshi
authors.initials: N
authors.lastname: Yoshinaga
authors.affiliation: From the Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan.
authors.forename: Kotaro
authors.initials: K
authors.lastname: Shirakawa
authors.affiliation: From the Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kobayashi
authors.affiliation: From the Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan.
authors.forename: Akifumi
authors.initials: A
authors.lastname: Takaori-Kondo
mesh_terms: D000071480:APOBEC-3G Deaminase / Q000235:genetics / Q000378:metabolism; D019943:Amino Acid Substitution; D000818:Animals; D002460:Cell Line; D050658:Core Binding Factor beta Subunit / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D020125:Mutation, Missense; D011485:Protein Binding; D055550:Protein Stability; D059748:Proteolysis; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation; D054320:vif Gene Products, Human Immunodeficiency Virus / Q000235:genetics / Q000378:metabolism*
chemical_list: C493692:CBFB protein, human; C493693:Cbfb protein, mouse; D050658:Core Binding Factor beta Subunit; D054320:vif Gene Products, Human Immunodeficiency Virus; C514847:vif protein, Human immunodeficiency virus 1; C497206:MDM2 protein, human; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2; D000071480:APOBEC-3G Deaminase; C464924:APOBEC3G protein, human; C496166:APOBEC3G protein, mouse
keywords: HIV; host-pathogen interaction; mouse double minute 2 homolog (MDM2); proteasome; protein-protein interaction; ubiquitin; viral protein