title: SKP2 is required for ubiquitin-mediated degradation of the CDK inhibitor p27.
abstract: Degradation of the mammalian cyclin-dependent kinase (CDK) inhibitor p27 is required for the cellular transition from quiescence to the proliferative state. The ubiquitination and subsequent degradation of p27 depend on its phosphorylation by cyclin-CDK complexes. However, the ubiquitin-protein ligase necessary for p27 ubiquitination has not been identified. Here we show that the F-box protein SKP2 specifically recognizes p27 in a phosphorylation-dependent manner that is characteristic of an F-box-protein-substrate interaction. Furthermore, both in vivo and in vitro, SKP2 is a rate-limiting component of the machinery that ubiquitinates and degrades phosphorylated p27. Thus, p27 degradation is subject to dual control by the accumulation of both SKP2 and cyclins following mitogenic stimulation.
authors.affiliation: Department of Pathology, New York University Medical Center, New York 10016, USA.
authors.forename: A C
authors.initials: AC
authors.lastname: Carrano
authors.forename: E
authors.initials: E
authors.lastname: Eytan
authors.forename: A
authors.initials: A
authors.lastname: Hershko
authors.forename: M
authors.initials: M
authors.lastname: Pagano
mesh_terms: D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors*; D004791:Enzyme Inhibitors / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D020319:Oligodeoxyribonucleotides, Antisense / Q000235:genetics / Q000494:pharmacology; D010766:Phosphorylation; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D044786:S-Phase Kinase-Associated Proteins; D025521:Tumor Suppressor Proteins; D014452:Ubiquitins / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D008869:Microtubule-Associated Proteins; D020319:Oligodeoxyribonucleotides, Antisense; D012333:RNA, Messenger; D044786:S-Phase Kinase-Associated Proteins; D025521:Tumor Suppressor Proteins; D014452:Ubiquitins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases