title: Regulation of cyclin-dependent kinase activity during mitotic exit and maintenance of genome stability by p21, p27, and p107.
abstract: To study the regulation of cyclin-dependent kinase (CDK) activity during mitotic exit in mammalian cells, we constructed murine cell lines that constitutively express a stabilized mutant of cyclin A (cyclin A47). Even though cyclin A47 was expressed throughout mitosis and in G1 cells, its associated CDK activity was inactivated after the transition from metaphase to anaphase. Cyclin A47 associated with both p21 and p27 during mitotic exit, implicating these proteins in CDK inactivation. However, cyclin A47 was fully inhibited during the M-to-G1 transition in p21(-/-) p27(-/-) fibroblasts. Also, the CDKs associated with cyclin A47 were not inactivated by phosphorylation at tyrosines. The protein responsible for CDK inactivation during mitotic exit in p21/p27 null cells was the Rb family member, p107. p107 bound to cyclin A47 when p21 and p27 were absent, and cyclin A47-CDK activity was not inactivated during the M-to-G1 transition in p21(-/-) p27(-/-) p107(-/-) null fibroblasts. Enforced expression of cyclin A in cells lacking all three CDK inhibitors induced rapid tetraploidization, indicative of mitotic failure/endoreduplication. We concluded that cyclin proteolysis and CDK inhibitors constitute redundant pathways that control cyclin A-CDK activity during mitotic exit in mammalian cells and that loss of these pathways can cause genetic instability.
authors.affiliation: Department of Bioscience, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo 156-8502, Japan. taku@nodai.ac.jp
authors.forename: Taku
authors.initials: T
authors.lastname: Chibazakura
authors.forename: Seth G
authors.initials: SG
authors.lastname: McGrew
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Cooper
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Yoshikawa
authors.forename: James M
authors.initials: JM
authors.lastname: Roberts
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D019925:Cyclin A / Q000737:chemistry / Q000378:metabolism; D056751:Cyclin A2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D016193:G1 Phase; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008840:Microfilament Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D008938:Mitosis / Q000235:genetics*; D009124:Muscle Proteins; D015739:Nocodazole / Q000494:pharmacology; D009687:Nuclear Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D016160:Retinoblastoma Protein / Q000378:metabolism; D050720:Retinoblastoma-Like Protein p107; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: C503721:CCNA2 protein, human; C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; D019925:Cyclin A; D056751:Cyclin A2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D008840:Microfilament Proteins; D009124:Muscle Proteins; D009687:Nuclear Proteins; C493844:RBL1 protein, human; C489485:Rbl1 protein, mouse; D016160:Retinoblastoma Protein; D050720:Retinoblastoma-Like Protein p107; C058992:Tagln protein, mouse; D018844:Cyclin-Dependent Kinases; D015739:Nocodazole