title: ALIX is a Lys63-specific polyubiquitin binding protein that functions in retrovirus budding.
abstract: The diversity of ubiquitin (Ub)-dependent signaling is attributed to the ability of this small protein to form different types of covalently linked polyUb chains and to the existence of Ub binding proteins that interpret this molecular syntax. We used affinity capture/mass spectrometry to identify ALIX, a component of the ESCRT pathway, as a Ub binding protein. We report that the V domain of ALIX binds directly and selectively to K63-linked polyUb chains, exhibiting a strong preference for chains composed of more than three Ub. Sequence analysis identified two potential Ub binding sites on a single α-helical surface within the coiled-coil region of the V domain. Mutation of these putative Ub binding sites inhibited polyUb binding to the isolated V domain in vitro and impaired budding of lentiviruses. These data reveal an important role for K63 polyUb binding by ALIX in retroviral release.
authors.affiliation: Department of Biology, Stanford University, Stanford, CA 94305, USA.
authors.forename: Dara P
authors.initials: DP
authors.lastname: Dowlatshahi
authors.forename: Virginie
authors.initials: V
authors.lastname: Sandrin
authors.forename: Sandro
authors.initials: S
authors.lastname: Vivona
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Shaler
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Kaiser
authors.forename: Francesco
authors.initials: F
authors.lastname: Melandri
authors.forename: Wesley I
authors.initials: WI
authors.lastname: Sundquist
authors.forename: Ron R
authors.initials: RR
authors.lastname: Kopito
mesh_terms: D001665:Binding Sites / Q000235:genetics; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D002460:Cell Line; D056827:Endosomal Sorting Complexes Required for Transport / Q000737:chemistry / Q000378:metabolism*; D057809:HEK293 Cells; D015497:HIV-1 / Q000502:physiology*; D006801:Humans; D004860:Infectious Anemia Virus, Equine / Q000502:physiology*; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D017433:Protein Structure, Secondary; D012190:Retroviridae / Q000502:physiology*; D015398:Signal Transduction; D025801:Ubiquitin / Q000737:chemistry / Q000378:metabolism*; D057074:Virus Release
chemical_list: D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D056827:Endosomal Sorting Complexes Required for Transport; C117020:PDCD6IP protein, human; D025801:Ubiquitin