title: Ubiquitination of BST-2 protein by HIV-1 Vpu protein does not require lysine, serine, or threonine residues within the BST-2 cytoplasmic domain.
abstract: The cellular protein BST-2/CD317/Tetherin has been shown to inhibit the release of HIV-1 and other enveloped viruses from infected cells. The HIV-1 accessory protein Vpu binds to both BST-2 and βTrCP, a substrate-recognition subunit for the SCF (Skip1-Cullin1-F-box protein) E3 ubiquitin ligase complex. This interaction leads to both the degradation of BST-2 and the enhancement of viral egress. Recently BST-2 was shown to be ubiquitinated in this process. Here we have confirmed the Vpu- and βTrCP-dependent multi/polyubiquitination of BST-2. Ubiquitinated BST-2 accumulated in cells treated with a lysosomal inhibitor but not a proteasomal inhibitor. Additionally, we observed that a BST-2 mutant deleted for its cytosolically exposed lysine residues is also ubiquitinated. Subsequent experiments suggested that Vpu promotes BST-2 ubiquitination upon amino acid residues bearing hydroxyl- but not thiol-bearing side chains. However, a BST-2 mutant bearing substitutions for its cytoplasmically exposed Ser, Thr, and Lys residues was still down-regulated, ubiquitinated, and degraded in a Vpu-dependent manner. Our results suggest that Vpu may target either the BST-2 cytoplasmic Tyr residues or the NH(2) terminus itself for ubiquitination.
authors.affiliation: Vaccine and Gene Therapy Institute, Oregon Health and Science University, Beaverton, Oregon 97006, USA. gustinj@ohsu.edu
authors.forename: Jean K
authors.initials: JK
authors.lastname: Gustin
authors.forename: Janet L
authors.initials: JL
authors.lastname: Douglas
authors.forename: Ying
authors.initials: Y
authors.lastname: Bai
authors.forename: Ashlee V
authors.initials: AV
authors.lastname: Moses
mesh_terms: D019943:Amino Acid Substitution; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D058851:GPI-Linked Proteins / Q000235:genetics / Q000378:metabolism; D015497:HIV-1 / Q000235:genetics / Q000378:metabolism*; D054298:Human Immunodeficiency Virus Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D020125:Mutation, Missense; D011485:Protein Binding; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism; D054875:Ubiquitination; D054334:Viral Regulatory and Accessory Proteins / Q000235:genetics / Q000378:metabolism*; D057074:Virus Release; D044844:beta-Transducin Repeat-Containing Proteins / Q000235:genetics / Q000378:metabolism; D000074010:Bone Marrow Stromal Antigen 2; D000086082:Viroporin Proteins
chemical_list: D015703:Antigens, CD; D058851:GPI-Linked Proteins; D054298:Human Immunodeficiency Virus Proteins; D044767:Ubiquitin-Protein Ligases; D054334:Viral Regulatory and Accessory Proteins; D044844:beta-Transducin Repeat-Containing Proteins; C094572:BST2 protein, human; D000074010:Bone Marrow Stromal Antigen 2; C514859:vpu protein, Human immunodeficiency virus 1; D000086082:Viroporin Proteins