title: Activation of extracellular signal-regulated kinase (ERK) in G2 phase delays mitotic entry through p21CIP1.
abstract: Extracellular signal-regulated kinase activity is essential for mediating cell cycle progression from G(1) phase to S phase (DNA synthesis). In contrast, the role of extracellular signal-regulated kinase during G(2) phase and mitosis (M phase) is largely undefined. Previous studies have suggested that inhibition of basal extracellular signal-regulated kinase activity delays G(2)- and M-phase progression. In the current investigation, we have examined the consequence of activating the extracellular signal-regulated kinase pathway during G(2) phase on subsequent progression through mitosis. Using synchronized HeLa cells, we show that activation of the extracellular signal-regulated kinase pathway with phorbol 12-myristate 13-acetate or epidermal growth factor during G(2) phase causes a rapid cell cycle arrest in G(2) as measured by flow cytometry, mitotic indices and cyclin B1 expression. This G(2)-phase arrest was reversed by pre-treatment with bisindolylmaleimide or U0126, which are selective inhibitors of protein kinase C proteins or the extracellular signal-regulated kinase activators, MEK1/2, respectively. The extracellular signal-regulated kinase-mediated delay in M-phase entry appeared to involve de novo synthesis of the cyclin-dependent kinase inhibitor, p21(CIP1), during G(2) through a p53-independent mechanism. To establish a function for the increased expression of p21(CIP1) and delayed cell cycle progression, we show that extracellular signal-regulated kinase activation in G(2)-phase cells results in an increased number of cells containing chromosome aberrations characteristic of genomic instability. The presence of chromosome aberrations following extracellular signal-regulated kinase activation during G(2)-phase was further augmented in cells lacking p21(CIP1). These findings suggest that p21(CIP1) mediated inhibition of cell cycle progression during G(2)/M phase protects against inappropriate activation of signalling pathways, which may cause excessive chromosome damage and be detrimental to cell survival.
authors.affiliation: Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland 21201, USA.
authors.forename: S
authors.initials: S
authors.lastname: Dangi
authors.forename: F M
authors.initials: FM
authors.lastname: Chen
authors.forename: P
authors.initials: P
authors.lastname: Shapiro
mesh_terms: D002070:Butadienes / Q000494:pharmacology; D043171:Chromosomal Instability; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000502:physiology*; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D016195:G2 Phase; D006367:HeLa Cells; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D048728:MAP Kinase Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048730:MAP Kinase Kinase Kinase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D008301:Maleimides / Q000494:pharmacology; D008938:Mitosis; D009570:Nitriles / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000502:physiology
chemical_list: D002070:Butadienes; C534699:CCNB1 protein, human; D019926:Cyclin B; D056744:Cyclin B1; D050759:Cyclin-Dependent Kinase Inhibitor p21; D007211:Indoles; D008301:Maleimides; D009570:Nitriles; D016159:Tumor Suppressor Protein p53; C113580:U 0126; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases; D048728:MAP Kinase Kinase Kinase 1; D048730:MAP Kinase Kinase Kinase 2; C088060:bisindolylmaleimide; D013755:Tetradecanoylphorbol Acetate