Vif hijacks CBF-β to degrade APOBEC3G and promote HIV-1 infection

Restriction factors, such as the retroviral complementary DNA deaminase APOBEC3G, are cellular proteins that dominantly block virus replication. The AIDS virus, human immunodeficiency virus type 1 (HIV-1), produces the accessory factor Vif, which counteracts the host’s antiviral defence by hijacking a ubiquitin ligase complex, containing CUL5, ELOC, ELOB and a RING-box protein, and targeting APOBEC3G for degradation. Here we reveal, using an affinity tag/purification mass spectrometry approach, that Vif additionally recruits the transcription cofactor CBF-β to this ubiquitin ligase complex. CBF-β, which normally functions in concert with RUNX DNA binding proteins, allows the reconstitution of a recombinant six-protein assembly that elicits specific polyubiquitination activity with APOBEC3G, but not the related deaminase APOBEC3A. Using RNA knockdown and genetic complementation studies, we also demonstrate that CBF-β is required for Vif-mediated degradation of APOBEC3G and therefore for preserving HIV-1 infectivity. Finally, simian immunodeficiency virus (SIV) Vif also binds to and requires CBF-β to degrade rhesus macaque APOBEC3G, indicating functional conservation. Methods of disrupting the CBF-β–Vif interaction might enable HIV-1 restriction and provide a supplement to current antiviral therapies that primarily target viral proteins.

[1]  B. Strack,et al.  Vif Overcomes the Innate Antiviral Activity of APOBEC3G by Promoting Its Degradation in the Ubiquitin-Proteasome Pathway* , 2004, Journal of Biological Chemistry.

[2]  W. Brown,et al.  Quantitative profiling of the full APOBEC3 mRNA repertoire in lymphocytes and tissues: implications for HIV-1 restriction , 2010, Nucleic acids research.

[3]  Tomoki Chiba,et al.  Interplay of transcription factors in T‐cell differentiation and function: the role of Runx , 2011, Immunology.

[4]  J. Goncalves,et al.  Phosphorylation of a novel SOCS-box regulates assembly of the HIV-1 Vif-Cul5 complex that promotes APOBEC3G degradation. , 2004, Genes & development.

[5]  Michael Emerman,et al.  HIV-1 accessory proteins--ensuring viral survival in a hostile environment. , 2008, Cell host & microbe.

[6]  M. Roussel,et al.  E2-RING expansion of the NEDD8 cascade confers specificity to cullin modification. , 2009, Molecular cell.

[7]  Raymond J. Deshaies,et al.  Mechanism of Lysine 48-Linked Ubiquitin-Chain Synthesis by the Cullin-RING Ubiquitin-Ligase Complex SCF-Cdc34 , 2005, Cell.

[8]  M. Malim,et al.  Defining APOBEC3 Expression Patterns in Human Tissues and Hematopoietic Cell Subsets , 2009, Journal of Virology.

[9]  Reuben S Harris,et al.  The Vif Protein of HIV Triggers Degradation of the Human Antiretroviral DNA Deaminase APOBEC3G , 2003, Current Biology.

[10]  Anjanabha Saha,et al.  Multimodal activation of the ubiquitin ligase SCF by Nedd8 conjugation , 2008, Molecular cell.

[11]  David O. Morgan,et al.  Sequential E2s Drive Polyubiquitin Chain Assembly on APC Targets , 2007, Cell.

[12]  D. Barford,et al.  Getting into position: the catalytic mechanisms of protein ubiquitylation. , 2004, The Biochemical journal.

[13]  Steven P Gygi,et al.  Certain Pairs of Ubiquitin-conjugating Enzymes (E2s) and Ubiquitin-Protein Ligases (E3s) Synthesize Nondegradable Forked Ubiquitin Chains Containing All Possible Isopeptide Linkages* , 2007, Journal of Biological Chemistry.

[14]  Tom Alber,et al.  Purification and characterization of HIV–human protein complexes , 2010, Methods.

[15]  M. Malim,et al.  The antiretroviral enzyme APOBEC3G is degraded by the proteasome in response to HIV-1 Vif , 2003, Nature Medicine.

[16]  John H. Morris,et al.  Global landscape of HIV–human protein complexes , 2011, Nature.

[17]  W. Greene,et al.  HIV-1 Vif blocks the antiviral activity of APOBEC3G by impairing both its translation and intracellular stability. , 2003, Molecular cell.

[18]  S. Goff.  Retrovirus restriction factors. , 2004, Molecular cell.

[19]  Yunkai Yu,et al.  Induction of APOBEC3G Ubiquitination and Degradation by an HIV-1 Vif-Cul5-SCF Complex , 2003, Science.

[20]  Martin Rechsteiner,et al.  Recognition of the polyubiquitin proteolytic signal , 2000, The EMBO journal.

[21]  Z. Pan,et al.  Priming and extending: a UbcH5/Cdc34 E2 handoff mechanism for polyubiquitination on a SCF substrate. , 2010, Molecular cell.

[22]  M. Stenglein,et al.  APOBEC3 proteins mediate the clearance of foreign DNA from human cells , 2010, Nature Structural &Molecular Biology.

[23]  R. Harris,et al.  Human Immunodeficiency Virus Type 1 Vif Induces Cell Cycle Delay via Recruitment of the Same E3 Ubiquitin Ligase Complex That Targets APOBEC3 Proteins for Degradation , 2008, Journal of Virology.

[24]  Y. Xiong,et al.  Structural Insight into the Human Immunodeficiency Virus Vif SOCS Box and Its Role in Human E3 Ubiquitin Ligase Assembly , 2008, Journal of Virology.

[25]  John S. Albin,et al.  Interactions of host APOBEC3 restriction factors with HIV-1 in vivo: implications for therapeutics , 2010, Expert Reviews in Molecular Medicine.

[26]  Lela Lackey,et al.  Human and Rhesus APOBEC3D, APOBEC3F, APOBEC3G, and APOBEC3H Demonstrate a Conserved Capacity To Restrict Vif-Deficient HIV-1 , 2011, Journal of Virology.

[27]  M. Malim,et al.  Isolation of a human gene that inhibits HIV-1 infection and is suppressed by the viral Vif protein , 2002, Nature.

[28]  Keiichi I Nakayama,et al.  VHL-box and SOCS-box domains determine binding specificity for Cul2-Rbx1 and Cul5-Rbx2 modules of ubiquitin ligases. , 2004, Genes & development.