title: Oct-1 potentiates CREB-driven cyclin D1 promoter activation via a phospho-CREB- and CREB binding protein-independent mechanism.
abstract: Cyclin D1, the regulatory subunit for mid-G(1) cyclin-dependent kinases, controls the expression of numerous cell cycle genes. A cyclic AMP-responsive element (CRE), located upstream of the cyclin D1 mRNA start site, integrates mitogenic signals that target the CRE-binding factor CREB, which can recruit the transcriptional coactivator CREB-binding protein (CBP). We describe an alternative mechanism for CREB-driven cyclin D1 induction that involves the ubiquitous POU domain protein Oct-1. In the breast cancer cell line MCF-7, overexpression of Oct-1 or its POU domain strongly increases transcriptional activation of cyclin D1 and GAL4 reporter genes that is specifically dependent upon CREB but independent of Oct-1 DNA binding. Gel retardation and chromatin immunoprecipitation assays confirm that POU forms a complex with CREB bound to the cyclin D1 CRE. In solution, CREB interaction with POU requires the CREB Q2 domain and, notably, occurs with CREB that is not phosphorylated on Ser 133. Accordingly, Oct-1 also potently enhances transcriptional activation mediated by a Ser133Ala CREB mutant. Oct-1/CREB synergy is not diminished by the adenovirus E1A 12S protein, a repressor of CBP coactivator function. In contrast, E1A strongly represses CBP-enhanced transactivation by CREB phosphorylated on Ser 133. Our observation that Oct-1 potentiates CREB-dependent cyclin D1 transcriptional activity independently of Ser 133 phosphorylation and E1A-sensitive coactivator function offers a new paradigm for the regulation of cyclin D1 induction by proliferative signals.
authors.affiliation: Institut de Génétique Moléculaire, CNRS, UMR 5535, IFR24, 34293 Montpellier Cedex 5, France.
authors.forename: Séverine
authors.initials: S
authors.lastname: Boulon
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Dantonel
authors.forename: Virginie
authors.initials: V
authors.lastname: Binet
authors.forename: Annick
authors.initials: A
authors.lastname: Vié
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Blanchard
authors.forename: Robert A
authors.initials: RA
authors.lastname: Hipskind
authors.forename: Alexandre
authors.initials: A
authors.lastname: Philips
mesh_terms: D001943:Breast Neoplasms; D050882:CREB-Binding Protein; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D019938:Cyclin D1 / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D017930:Genes, Reporter; D051863:Host Cell Factor C1; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism*; D050811:Octamer Transcription Factor-1; D010750:Phosphoproteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; C497692:HCFC1 protein, human; D051863:Host Cell Factor C1; D009687:Nuclear Proteins; D050811:Octamer Transcription Factor-1; C494165:POU2F1 protein, human; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D019938:Cyclin D1; D050882:CREB-Binding Protein; C494363:CREBBP protein, human