title: Activation of cyclin D1 expression by the ERK5 cascade.
abstract: Transcriptional activation of the cyclin D1 gene is a key step in cell proliferation. Accordingly, cyclin D1 overexpression is frequently an early step in neoplastic transformation, particularly in mammary epithelium. Numerous studies have linked elevated cyclin D1 promoter activity to a sustained activation of the ERK1/2 cascade. Here we show that the ERK5 cascade, a distinct mitogen-induced MAPK pathway, can also drive cyclin D1 expression. In CCL39 cells, serum induces a strong, prolonged peak of ERK1/2 and ERK5 phosphorylation, and subsequently elevates cyclin D1 mRNA and protein levels. Overexpression of constitutively active MEK5 and wt ERK5 induces a cyclin D1 reporter gene (D1 -973-luciferase) at least as well as constitutively active MEK1. Activation is blocked by kinase-dead mutants of ERK5 and ERK2, respectively. Mutation of the CRE at -50 in the cyclin D1 promoter decreases activation by the ERK5 but not the ERK1/2 cascade. Importantly, expression of kinase-dead ERK5 diminishes endogenous cyclin D1 protein induction by serum in CCL39 cells and the breast cancer cell lines MCF-7 and HS579. These data identify the cyclin D1 gene as a novel target of the ERK5 cascade, an observation with important implications in cancers involving cyclin D1 deregulation.
authors.affiliation: Institut de Génétique Moléculaire de Montpellier, CNRS, UMR 5535, IFR 122, 1919 Route de Mende, 34293 Montpellier 5, France.
authors.forename: Roseann
authors.initials: R
authors.lastname: Mulloy
authors.forename: Sara
authors.initials: S
authors.lastname: Salinas
authors.forename: Alexandre
authors.initials: A
authors.lastname: Philips
authors.forename: Robert A
authors.initials: RA
authors.lastname: Hipskind
mesh_terms: D001943:Breast Neoplasms; D019938:Cyclin D1 / Q000096:biosynthesis / Q000235:genetics*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D048054:Mitogen-Activated Protein Kinase 7; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
chemical_list: D019938:Cyclin D1; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048054:Mitogen-Activated Protein Kinase 7; D020928:Mitogen-Activated Protein Kinases