title: HIV/simian immunodeficiency virus (SIV) accessory virulence factor Vpx loads the host cell restriction factor SAMHD1 onto the E3 ubiquitin ligase complex CRL4DCAF1.
abstract: The sterile alpha motif and HD domain-containing protein-1 (SAMHD1) inhibits infection of myeloid cells by human and related primate immunodeficiency viruses (HIV and SIV). This potent inhibition is counteracted by the Vpx accessory virulence factor of HIV-2/SIVsm viruses, which targets SAMHD1 for proteasome-dependent degradation, by reprogramming cellular CRL4(DCAF1) E3 ubiquitin ligase. However, the precise mechanism of Vpx-dependent recruitment of human SAMHD1 onto the ligase, and the molecular interfaces on the respective molecules have not been defined. Here, we show that human SAMHD1 is recruited to the CRL4(DCAF1-Vpx) E3 ubiquitin ligase complex by interacting with the DCAF1 substrate receptor subunit in a Vpx-dependent manner. No stable association is detectable with DCAF1 alone. The SAMHD1 determinant for the interaction is a short peptide located distal to the SAMHD1 catalytic domain and requires the presence of Vpx for stable engagement. This peptide is sufficient to confer Vpx-dependent recruitment to CRL4(DCAF1) and ubiquitination when fused to heterologous proteins. The precise amino acid sequence of the peptide diverges among SAMHD1 proteins from different vertebrate species, explaining selective down-regulation of human SAMHD1 levels by Vpx. Critical amino acid residues of SAMHD1 and Vpx involved in the DCAF1-Vpx-SAMDH1 interaction were identified by mutagenesis. Our findings show that the N terminus of Vpx, bound to DCAF1, recruits SAMHD1 via its C terminus to CRL4, in a species-specific manner for proteasomal degradation.
authors.affiliation: Department of Structural Biology and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260, USA.
authors.forename: Jinwoo
authors.initials: J
authors.lastname: Ahn
authors.forename: Caili
authors.initials: C
authors.lastname: Hao
authors.forename: Junpeng
authors.initials: J
authors.lastname: Yan
authors.forename: Maria
authors.initials: M
authors.lastname: DeLucia
authors.forename: Jennifer
authors.initials: J
authors.lastname: Mehrens
authors.forename: Chuanping
authors.initials: C
authors.lastname: Wang
authors.forename: Angela M
authors.initials: AM
authors.lastname: Gronenborn
authors.forename: Jacek
authors.initials: J
authors.lastname: Skowronski
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D002352:Carrier Proteins / Q000378:metabolism*; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism; D015536:Down-Regulation; D057809:HEK293 Cells; D054884:Host-Pathogen Interactions; D006801:Humans; D008969:Molecular Sequence Data; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000378:metabolism*; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D017346:Protein Serine-Threonine Kinases; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D000076106:SAM Domain and HD Domain-Containing Protein 1; D015302:Simian Immunodeficiency Virus / Q000502:physiology*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D054334:Viral Regulatory and Accessory Proteins / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; C091435:DDB1 protein, human; D004268:DNA-Binding Proteins; C429530:DTL protein, human; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; C513059:VPX protein, Simian immunodeficiency virus; D054334:Viral Regulatory and Accessory Proteins; D044767:Ubiquitin-Protein Ligases; C530533:DCAF1 protein, human; D017346:Protein Serine-Threonine Kinases; D000076106:SAM Domain and HD Domain-Containing Protein 1; C484280:SAMHD1 protein, human; D020559:Monomeric GTP-Binding Proteins