title: VWA domain of S5a restricts the ability to bind ubiquitin and Ubl to the 26S proteasome.
abstract: The 26S proteasome recognizes a vast number of ubiquitin-dependent degradation signals linked to various substrates. This recognition is mediated mainly by the stoichiometric proteasomal resident ubiquitin receptors S5a and Rpn13, which harbor ubiquitin-binding domains. Regulatory steps in substrate binding, processing, and subsequent downstream proteolytic events by these receptors are poorly understood. Here we demonstrate that mammalian S5a is present in proteasome-bound and free states. S5a is required for efficient proteasomal degradation of polyubiquitinated substrates and the recruitment of ubiquitin-like (Ubl) harboring proteins; however, S5a-mediated ubiquitin and Ubl binding occurs only on the proteasome itself. We identify the VWA domain of S5a as a domain that limits ubiquitin and Ubl binding to occur only upon proteasomal association. Multiubiquitination events within the VWA domain can further regulate S5a association. Our results provide a molecular explanation to how ubiquitin and Ubl binding to S5a is restricted to the 26S proteasome.
authors.affiliation: Department of Biochemistry, Rappaport Family Institute for Research in the Medical Sciences, Technion-Israel Institute of Technology, Haifa 31096, Israel.
authors.forename: Ravit
authors.initials: R
authors.lastname: Piterman
authors.affiliation: Department of Biochemistry, Rappaport Family Institute for Research in the Medical Sciences, Technion-Israel Institute of Technology, Haifa 31096, Israel.
authors.forename: Ilana
authors.initials: I
authors.lastname: Braunstein
authors.affiliation: Department of Biochemistry, Rappaport Family Institute for Research in the Medical Sciences, Technion-Israel Institute of Technology, Haifa 31096, Israel.
authors.forename: Elada
authors.initials: E
authors.lastname: Isakov
authors.affiliation: Smoler Proteomics Center, Technion-Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Tamar
authors.initials: T
authors.lastname: Ziv
authors.affiliation: Department of Biological Regulation, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Ami
authors.initials: A
authors.lastname: Navon
authors.affiliation: Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Shenhav
authors.initials: S
authors.lastname: Cohen
authors.affiliation: Department of Biochemistry, Rappaport Family Institute for Research in the Medical Sciences, Technion-Israel Institute of Technology, Haifa 31096, Israel stanhill@tx.technion.ac.il.
authors.forename: Ariel
authors.initials: A
authors.lastname: Stanhill
mesh_terms: D051701:Activating Transcription Factor 4 / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D025821:Polyubiquitin / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D059748:Proteolysis; D016601:RNA-Binding Proteins; D025801:Ubiquitin / Q000378:metabolism*; D057149:Ubiquitinated Proteins / Q000378:metabolism; D054875:Ubiquitination
chemical_list: C497109:ATF4 protein, human; C498506:PSMD4 protein, human; D016601:RNA-Binding Proteins; D025801:Ubiquitin; D057149:Ubiquitinated Proteins; D025821:Polyubiquitin; D051701:Activating Transcription Factor 4; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease