title: USP19 deubiquitinating enzyme supports cell proliferation by stabilizing KPC1, a ubiquitin ligase for p27Kip1.
abstract: p27(Kip1) is a cyclin-dependent kinase inhibitor that regulates the G(1)/S transition. Increased degradation of p27(Kip1) is associated with cellular transformation. Previous work demonstrated that the ubiquitin ligases KPC1/KPC2 and SCF(Skp2) ubiquitinate p27(Kip1) in G(1) and early S, respectively. The regulation of these ligases remains unclear. We report here that the USP19 deubiquitinating enzyme interacts with and stabilizes KPC1, thereby modulating p27(Kip1) levels and cell proliferation. Cells depleted of USP19 by RNA interference exhibited an inhibition of cell proliferation, progressing more slowly from G(0)/G1 to S phase, and accumulated p27(Kip1). This increase in p27(Kip1) was associated with normal levels of Skp2 but reduced levels of KPC1. The overexpression of KPC1 or the use of p27(-/-) cells inhibited significantly the growth defect observed upon USP19 depletion. KPC1 was ubiquitinated in vivo and stabilized by proteasome inhibitors and by overexpression of USP19, and it also coimmunoprecipitated with USP19. Our results identify USP19 as the first deubiquitinating enzyme that regulates the stability of a cyclin-dependent kinase inhibitor and demonstrate that progression through G(1) to S phase is, like the metaphase-anaphase transition, controlled in a hierarchical, multilayered fashion.
authors.affiliation: Polypeptide Laboratory, Division of Endocrinology and Metabolism, Department of Medicine, McGill University, Montreal, Quebec, Canada.
authors.forename: Yu
authors.initials: Y
authors.lastname: Lu
authors.forename: Olasunkanmi A J
authors.initials: OA
authors.lastname: Adegoke
authors.forename: Alain
authors.initials: A
authors.lastname: Nepveu
authors.forename: Keiichi I
authors.initials: KI
authors.lastname: Nakayama
authors.forename: Nathalie
authors.initials: N
authors.lastname: Bedard
authors.forename: Dongmei
authors.initials: D
authors.lastname: Cheng
authors.forename: Junmin
authors.initials: J
authors.lastname: Peng
authors.forename: Simon S
authors.initials: SS
authors.lastname: Wing
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism; D002460:Cell Line; D049109:Cell Proliferation; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism*; D015151:Immunoblotting; D051379:Mice; D034622:RNA Interference; D051381:Rats; D044786:S-Phase Kinase-Associated Proteins / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism*; D043222:Ubiquitin Thiolesterase / Q000235:genetics / Q000378:metabolism*; D043743:Ubiquitin-Protein Ligase Complexes; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D044786:S-Phase Kinase-Associated Proteins; C558223:Ubac1 protein, rat; D025801:Ubiquitin; D050760:Cyclin-Dependent Kinase Inhibitor p27; D043743:Ubiquitin-Protein Ligase Complexes; D044767:Ubiquitin-Protein Ligases; D043222:Ubiquitin Thiolesterase