title: ERK1/2 and p38 cooperate to delay progression through G1 by promoting cyclin D1 protein turnover.
abstract: The conditional kinase DeltaMEKK3:ER allows activation of JNK, p38 and ERK1/2 without overt cellular stress or damage and has proved useful in understanding how these pathways regulate apoptosis and cell cycle progression. We have previously shown that activation of DeltaMEKK3:ER causes a sustained G(1) cell cycle arrest which requires p21(CIP1), with ERK1/2 and p38 cooperating to promote p21(CIP1) expression. In cells lacking p21(CIP1), DeltaMEKK3:ER causes only a transient delay in cell cycle re-entry. We now show that this delay in cell cycle re-entry is due to a reduction in cyclin D1 levels. Activation of DeltaMEKK3:ER promotes the proteasome-dependent turnover of cyclin D1; this requires phosphorylation of threonine 286 (T(286)) and expression of cyclin D1T(286)A rescues the delay in G(1)/S progression. DeltaMEKK3:ER-dependent phosphorylation of T(286) does not appear to be mediated by GSK3beta but requires activation of the ERK1/2 and p38 pathways. ERK1/2 can physically associate with cyclin D1 but activation of ERK1/2 alone is not sufficient for phosphorylation of T(286). Rather, cyclin D1 phosphorylation appears to require coincident activation of ERK1/2 and p38. Thus activation of DeltaMEKK3:ER promotes a sustained G(1) cell cycle arrest by a bipartite mechanism involving the rapid destruction of cyclin D1 and the slower more prolonged expression of p21(CIP1). This has parallels with the bipartite response to ionizing radiation and p53-independent mechanisms of G(1) cell cycle arrest in simple organisms such as yeast.
authors.affiliation: Laboratory of Molecular Signalling, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, England, UK.
authors.forename: Ruth M
authors.initials: RM
authors.lastname: Densham
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Todd
authors.forename: Kathy
authors.initials: K
authors.lastname: Balmanno
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Cook
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D002460:Cell Line; D019938:Cyclin D1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D015536:Down-Regulation; D004789:Enzyme Activation; D016193:G1 Phase; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation; D010769:Phosphothreonine / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D048490:raf Kinases / Q000378:metabolism
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D012333:RNA, Messenger; D010769:Phosphothreonine; D019938:Cyclin D1; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D048490:raf Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D038362:Glycogen Synthase Kinase 3; D046988:Proteasome Endopeptidase Complex