title: E2F proteins regulate MYCN expression in neuroblastomas.
abstract: Amplification of the MYCN gene, resulting in overexpression of MYCN, distinguishes a subset of neuroblastomas with poor prognosis. The transcription factors driving MYCN expression in neuroblastomas are unknown. In transient-transfection assays, E2F-1, E2F-2, and E2F-3 activate a MYCN reporter construct dependent on the presence of several putative E2F-binding sites. Using chromatin immunoprecipitation, we show that E2F-1, E2F-2, and E2F-3 bind to the proximal MYCN promoter in vivo, specifically in neuroblastoma cell lines expressing MYCN. Inhibition of E2F activity in MYCN-amplified cells by the overexpression of p16(INK4A) reduced MYCN expression. In addition, we provide evidence that E2F proteins are involved in the negative regulation of MYCN by TGF-beta and retinoic acid. These data suggest that E2F transcription factors are critical for both the full activation and the repression of MYCN in neuroblastomas.
authors.affiliation: Institute of Molecular Biology and Tumor Research (IMT), Emil-Mannkopff-Strasse 2, 35033 Marburg, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Strieder
authors.forename: Werner
authors.initials: W
authors.lastname: Lutz
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D018797:Cell Cycle Proteins; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D050703:E2F2 Transcription Factor; D050699:E2F3 Transcription Factor; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D000071447:N-Myc Proto-Oncogene Protein; D009447:Neuroblastoma; D009687:Nuclear Proteins / Q000235:genetics*; D015513:Oncogene Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D014212:Tretinoin / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D018797:Cell Cycle Proteins; D019941:Cyclin-Dependent Kinase Inhibitor p16; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D050703:E2F2 Transcription Factor; C493761:E2F2 protein, human; D050699:E2F3 Transcription Factor; C098319:E2F3 protein, human; C459801:MYCN protein, human; D000071447:N-Myc Proto-Oncogene Protein; D009687:Nuclear Proteins; D015513:Oncogene Proteins; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D014212:Tretinoin