title: The ubiquitin E3 ligase MARCH7 is differentially regulated by the deubiquitylating enzymes USP7 and USP9X.
abstract: Protein modification by one or more ubiquitin chains serves a critical signalling function across a wide range of cellular processes. Specificity within this system is conferred by ubiquitin E3 ligases, which target the substrates. Their activity is balanced by deubiquitylating enzymes (DUBs), which remove ubiquitin from both substrates and ligases. The RING-CH ligases were initially identified as viral immunoevasins involved in the downregulation of immunoreceptors. Their cellular orthologues, the Membrane-Associated RING-CH (MARCH) family represent a subgroup of the classical RING genes. Unlike their viral counterparts, the cellular RING-CH proteins appear highly regulated, and one of these in particular, MARCH7, was of interest because of a potential role in neuronal development and lymphocyte proliferation. Difficulties in detection and expression of this orphan ligase lead us to search for cellular cofactors involved in MARCH7 stability. In this study, we show that MARCH7 readily undergoes autoubiquitylation and associates with two deubiquitylating enzymes - ubiquitin-specific protease (USP)9X in the cytosol and USP7 in the nucleus. Exogenous expression and short interfering RNA depletion experiments demonstrate that MARCH7 can be stabilized by both USP9X and USP7, which deubiquitylate MARCH7 in the cytosol and nucleus, respectively. We therefore demonstrate compartment-specific regulation of this E3 ligase through recruitment of site-specific DUBs.
authors.affiliation: Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, CB2 0XY, UK.
authors.forename: James A
authors.initials: JA
authors.lastname: Nathan
authors.forename: Soma
authors.initials: S
authors.lastname: Sengupta
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Wood
authors.forename: Arie
authors.initials: A
authors.lastname: Admon
authors.forename: Gabriel
authors.initials: G
authors.lastname: Markson
authors.forename: Chris
authors.initials: C
authors.lastname: Sanderson
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Lehner
mesh_terms: D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation; D005786:Gene Expression Regulation; D006801:Humans; D016086:Lentivirus / Q000378:metabolism; D008214:Lymphocytes / Q000166:cytology; D051379:Mice; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence / Q000379:methods; D009474:Neurons / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D043222:Ubiquitin Thiolesterase / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D000076084:Ubiquitin-Specific Peptidase 7
chemical_list: D034741:RNA, Small Interfering; C506234:USP9X protein, human; C517824:MARCHF7 protein, human; D044767:Ubiquitin-Protein Ligases; C464569:USP7 protein, human; D043222:Ubiquitin Thiolesterase; D000076084:Ubiquitin-Specific Peptidase 7