title: Mutant MyoD lacking Cdc2 phosphorylation sites delays M-phase entry.
abstract: The transcription factors MyoD and Myf-5 control myoblast identity and differentiation. MyoD and Myf-5 manifest opposite cell cycle-specific expression patterns. Here, we provide evidence that MyoD plays a pivotal role at the G(2)/M transition by controlling the expression of p21(Waf1/Cip1) (p21), which is believed to regulate cyclin B-Cdc2 kinase activity in G(2). In growing myoblasts, MyoD reaccumulates during G(2) concomitantly with p21 before entry into mitosis; MyoD is phosphorylated on Ser5 and Ser200 by cyclin B-Cdc2, resulting in a decrease of its stability and down-regulation of both MyoD and p21. Inducible expression of a nonphosphorylable MyoD A5/A200 enhances the MyoD interaction with the coactivator P/CAF, thereby stimulating the transcriptional activation of a luciferase reporter gene placed under the control of the p21 promoter. MyoD A5/A200 causes sustained p21 expression, which inhibits cyclin B-Cdc2 kinase activity in G(2) and delays M-phase entry. This G(2) arrest is not observed in p21(-/-) cells. These results show that in cycling cells MyoD functions as a transcriptional activator of p21 and that MyoD phosphorylation is required for G(2)/M transition.
authors.affiliation: Laboratoire de Génétique Oncologique, Institut Gustave Roussy, 94805 Villejuif, France.
authors.forename: Lionel A J
authors.initials: LA
authors.lastname: Tintignac
authors.forename: Valentina
authors.initials: V
authors.lastname: Sirri
authors.forename: Marie Pierre
authors.initials: MP
authors.lastname: Leibovitch
authors.forename: Yann
authors.initials: Y
authors.lastname: Lécluse
authors.forename: Maria
authors.initials: M
authors.lastname: Castedo
authors.forename: Didier
authors.initials: D
authors.lastname: Metivier
authors.forename: Guido
authors.initials: G
authors.lastname: Kroemer
authors.forename: Serge A
authors.initials: SA
authors.lastname: Leibovitch
mesh_terms: D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D002460:Cell Line; D019926:Cyclin B / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D016195:G2 Phase; D005786:Gene Expression Regulation; D056284:Histone Deacetylase 1; D006655:Histone Deacetylases; D051379:Mice; D008938:Mitosis; D008954:Models, Biological; D018482:Muscle, Skeletal; D009154:Mutation / Q000235:genetics*; D017570:MyoD Protein / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D032446:Myoblasts / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D011485:Protein Binding; D013997:Time Factors; D015533:Transcriptional Activation
chemical_list: C493957:Cdkn1a protein, mouse; D019926:Cyclin B; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D017570:MyoD Protein; D010768:Phosphoserine; D016203:CDC2 Protein Kinase; C110550:HDAC1 protein, human; D056284:Histone Deacetylase 1; D006655:Histone Deacetylases