title: Mechanisms of primary and secondary estrogen target gene regulation in breast cancer cells.
abstract: Estrogen receptors (ERs), which mediate the proliferative action of estrogens in breast cancer cells, are ligand-dependent transcription factors that regulate expression of their primary target genes through several mechanisms. In addition to direct binding to cognate DNA sequences, ERs can be recruited to DNA through other transcription factors (tethering), or affect gene transcription through modulation of signaling cascades by non-genomic mechanisms of action. To better characterize the mechanisms of gene regulation by estrogens, we have identified more than 700 putative primary and about 1300 putative secondary target genes of estradiol in MCF-7 cells through microarray analysis performed in the presence or absence of the translation inhibitor cycloheximide. Although siRNA-mediated inhibition of ERalpha expression antagonized the effects of estradiol on up- and down-regulated primary target genes, estrogen response elements (EREs) were enriched only in the vicinity of up-regulated genes. Binding sites for several other transcription factors, including proteins known to tether ERalpha, were enriched in up- and/or down-regulated primary targets. Secondary estrogen targets were particularly enriched in sites for E2F family members, several of which were transcriptionally regulated by estradiol, consistent with a major role of these factors in mediating the effects of estrogens on gene expression and cellular growth.
authors.affiliation: Institute for Research in Immunology and Cancer and Biochemistry Department, Université de Montréal, C.P. 6128 Succursale Centre Ville, Montréal, QC H3C 3J7, Canada.
authors.forename: Véronique
authors.initials: V
authors.lastname: Bourdeau
authors.forename: Julie
authors.initials: J
authors.lastname: Deschênes
authors.forename: David
authors.initials: D
authors.lastname: Laperrière
authors.forename: Malika
authors.initials: M
authors.lastname: Aid
authors.forename: John H
authors.initials: JH
authors.lastname: White
authors.forename: Sylvie
authors.initials: S
authors.lastname: Mader
mesh_terms: D001665:Binding Sites; D001943:Breast Neoplasms / Q000235:genetics*; D045744:Cell Line, Tumor; D050684:E2F Transcription Factors / Q000378:metabolism; D004958:Estradiol / Q000494:pharmacology*; D047628:Estrogen Receptor alpha / Q000378:metabolism*; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D020218:Response Elements; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D050684:E2F Transcription Factors; D047628:Estrogen Receptor alpha; D004967:Estrogens; D014157:Transcription Factors; D004958:Estradiol