title: Serine-threonine ubiquitination mediates downregulation of BST-2/tetherin and relief of restricted virion release by HIV-1 Vpu.
abstract: The HIV-1 protein Vpu counteracts the antiviral activity of the innate restriction factor BST-2/tetherin by a mechanism that partly depends on its interaction with β-TrCP, a substrate adaptor for an SCF (Skp-Cullin 1-F box) E3 ubiquitin ligase complex. This suggests that Vpu stimulates the ubiquitination of BST-2 and that this underlies the relief of restriction. Here, we show that Vpu stimulates ubiquitination of BST-2. Mutation of all potential ubiquitination sites in the cytoplasmic domain of BST-2, including lysines, cysteines, serines, and threonines, abrogates Vpu-mediated ubiquitination. However, a serine-threonine-serine sequence specifically mediates the downregulation of BST-2 from the cell surface and the optimal relief of restricted virion release. Serine-threonine ubiquitination of BST-2 is likely part of the mechanism by which Vpu counteracts innate defenses.
authors.affiliation: Department of Medicine University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0679, USA. andrey.a.tokarev@gmail.com
authors.forename: Andrey A
authors.initials: AA
authors.lastname: Tokarev
authors.forename: Jason
authors.initials: J
authors.lastname: Munguia
authors.forename: John C
authors.initials: JC
authors.lastname: Guatelli
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D058851:GPI-Linked Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D015497:HIV-1 / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity; D054298:Human Immunodeficiency Virus Proteins / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D012694:Serine / Q000378:metabolism; D013912:Threonine / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism*; D054334:Viral Regulatory and Accessory Proteins / Q000378:metabolism*; D014771:Virion / Q000378:metabolism; D057074:Virus Release / Q000502:physiology*; 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; D012694:Serine; D013912:Threonine; D025801:Ubiquitin; 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