title: p21(Cip1) Promotes cyclin D1 nuclear accumulation via direct inhibition of nuclear export.
abstract: There is increasing evidence that p21(Cip1) and p27(Kip1) are requisite positive regulators of cyclin D1.CDK4 assembly and nuclear accumulation. Both Cip and Kip proteins can promote nuclear accumulation of cyclin D1, but the underlying mechanism has not been elucidated. We now provide evidence that p21(Cip1) promotes the nuclear accumulation of cyclin D1 complexes via inhibition of cyclin D1 nuclear export. In vivo, we demonstrate that p21(Cip1) can inhibit glycogen synthase kinase 3 beta-triggered cyclin D1 nuclear export and phosphorylation-dependent nucleocytoplasmic shuttling. Furthermore, we find that cyclin D1 nuclear accumulation in p21/p27 null cells can be restored through inhibition of CRM1-dependent nuclear export. The ability of p21(Cip1) to inhibit cyclin D1 nuclear export correlates with its ability to bind to Thr-286-phosphorylated cyclin D1 and thereby prevents cyclin D1.CRM1 association.
authors.affiliation: Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198, USA.
authors.forename: Jodi R
authors.initials: JR
authors.lastname: Alt
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Gladden
authors.forename: J Alan
authors.initials: JA
authors.lastname: Diehl
mesh_terms: D016475:3T3 Cells; D021581:Active Transport, Cell Nucleus; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002455:Cell Division; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D019938:Cyclin D1 / Q000378:metabolism*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D006801:Humans; D015151:Immunoblotting; D007313:Insecta; D051379:Mice; D008856:Microscopy, Fluorescence; D010766:Phosphorylation; D011485:Protein Binding; D013912:Threonine / Q000378:metabolism; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
chemical_list: C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; C493961:Cdkn1b protein, mouse; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D025521:Tumor Suppressor Proteins; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27; D013912:Threonine; D038341:Glycogen Synthase Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3