title: Phosphorylation of p27Kip1 on serine 10 is required for its binding to CRM1 and nuclear export.
abstract: Phosphorylation of the cyclin-dependent kinase inhibitor p27(Kip1) has been thought to regulate its stability. Ser(10) is the major phosphorylation site of p27(Kip1), and phosphorylation of this residue affects protein stability. Phosphorylation of p27(Kip1) on Ser(10) has now been shown to be required for the binding of CRM1, a carrier protein for nuclear export. The p27(Kip1) protein was translocated from the nucleus to the cytoplasm at the G(0)-G(1) transition of the cell cycle, and this export was inhibited by leptomycin B, a specific inhibitor of CRM1-dependent nuclear export. The nuclear export and subsequent degradation of p27(Kip1) at the G(0)-G(1) transition were observed in cells lacking Skp2, the F-box protein component of an SCF ubiquitin ligase complex, indicating that these early events are independent of Skp2-mediated proteolysis. Substitution of Ser(10) with Ala (S10A) markedly reduced the extent of p27(Kip1) export, whereas substitution of Ser(10) with Asp (S10D) or Glu (S10E) promoted export. Co-immunoprecipitation analysis showed that CRM1 preferentially interacted with S10D and S10E but not with S10A, suggesting that the phosphorylation of p27(Kip1) on Ser(10) is required for its binding to CRM1 and for its subsequent nuclear export.
authors.affiliation: Departments of Molecular and Cellular Biology and Molecular Genetics, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka 812-8582, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Ishida
authors.forename: Taichi
authors.initials: T
authors.lastname: Hara
authors.forename: Takumi
authors.initials: T
authors.lastname: Kamura
authors.forename: Minoru
authors.initials: M
authors.lastname: Yoshida
authors.forename: Keiko
authors.initials: K
authors.lastname: Nakayama
authors.forename: Keiichi I
authors.initials: KI
authors.lastname: Nakayama
mesh_terms: D016475:3T3 Cells; D000818:Animals; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D050760:Cyclin-Dependent Kinase Inhibitor p27; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D016193:G1 Phase; D006801:Humans; D006868:Hydrolysis; D051379:Mice; D010766:Phosphorylation; D011485:Protein Binding; D021381:Protein Transport; D016192:Resting Phase, Cell Cycle; D012694:Serine / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: C493961:Cdkn1b protein, mouse; D018797:Cell Cycle Proteins; D005231:Fatty Acids, Unsaturated; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D012694:Serine; C038753:leptomycin B