title: Degradation of p57Kip2 mediated by SCFSkp2-dependent ubiquitylation.
abstract: The abundance of the cyclin-dependent kinase (CDK) inhibitor p57Kip2, an important regulator of cell cycle progression, is thought to be controlled by the ubiquitin-proteasome pathway. The Skp1/Cul1/F-box (SCF)-type E3 ubiquitin ligase complex SCFSkp2 has now been shown to be responsible for regulating the cellular level of p57Kip2 by targeting it for ubiquitylation and proteolysis. The elimination of p57Kip2 was impaired in Skp2-/- cells, resulting in abnormal accumulation of the protein. Coimmunoprecipitation analysis also revealed that Skp2 interacts with p57Kip2 in vivo. Overexpression of WT Skp2 promoted degradation of p57Kip2, whereas expression of a dominant negative mutant of Skp2 prolonged the half-life of p57Kip2. Mutation of the threonine residue (Thr-310) of human p57Kip2 that is conserved between the COOH-terminal QT domains of p57Kip2 and p27Kip1 prevented the effect of Skp2 on the stability of p57Kip2, suggesting that phosphorylation at this site is required for SCFSkp2-mediated ubiquitylation. Finally, the purified recombinant SCFSkp2 complex mediated p57Kip2 ubiquitylation in vitro in a manner dependent on the presence of the cyclin E-CDK2 complex. These observations thus demonstrate that the SCFSkp2 complex plays an important role in cell-cycle progression by determining the abundance of p57Kip2 and that of the related CDK inhibitor p27Kip1.
authors.affiliation: Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka 812-8582, Japan.
authors.forename: Takumi
authors.initials: T
authors.lastname: Kamura
authors.forename: Taichi
authors.initials: T
authors.lastname: Hara
authors.forename: Shuhei
authors.initials: S
authors.lastname: Kotoshiba
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Yada
authors.forename: Noriko
authors.initials: N
authors.lastname: Ishida
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Imaki
authors.forename: Shigetsugu
authors.initials: S
authors.lastname: Hatakeyama
authors.forename: Keiko
authors.initials: K
authors.lastname: Nakayama
authors.forename: Keiichi I
authors.initials: KI
authors.lastname: Nakayama
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000502:physiology; D050760:Cyclin-Dependent Kinase Inhibitor p27; D050761:Cyclin-Dependent Kinase Inhibitor p57; D018844:Cyclin-Dependent Kinases / Q000502:physiology; D003546:Cysteine Endopeptidases / Q000502:physiology; D005260:Female; D006207:Half-Life; D006367:HeLa Cells; D006801:Humans; D008025:Ligases / Q000502:physiology*; D051379:Mice; D009097:Multienzyme Complexes / Q000502:physiology; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex; D025521:Tumor Suppressor Proteins / Q000502:physiology; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases
chemical_list: C493964:CDKN1C protein, human; C493961:Cdkn1b protein, mouse; C493965:Cdkn1c protein, mouse; D018797:Cell Cycle Proteins; D050761:Cyclin-Dependent Kinase Inhibitor p57; D009097:Multienzyme Complexes; D009687:Nuclear Proteins; D025521:Tumor Suppressor Proteins; D025801:Ubiquitin; D050760:Cyclin-Dependent Kinase Inhibitor p27; D044767:Ubiquitin-Protein Ligases; D018844:Cyclin-Dependent Kinases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D008025:Ligases