title: Estrogen regulation and physiopathologic significance of alternative promoters in breast cancer.
abstract: Alternative promoters (AP) occur in >30% protein-coding genes and contribute to proteome diversity. However, large-scale analyses of AP regulation are lacking, and little is known about their potential physiopathologic significance. To better understand the transcriptomic effect of estrogens, which play a major role in breast cancer, we analyzed gene and AP regulation by estradiol in MCF7 cells using pan-genomic exon arrays. We thereby identified novel estrogen-regulated genes (ERG) and determined the regulation of AP-encoded transcripts in 150 regulated genes. In <30% cases, APs were regulated in a similar manner by estradiol, whereas in >70% cases, they were regulated differentially. The patterns of AP regulation correlated with the patterns of estrogen receptor alpha (ERalpha) and CCCTC-binding factor (CTCF) binding sites at regulated gene loci. Interestingly, among genes with differentially regulated (DR) APs, we identified cases where estradiol regulated APs in an opposite manner, sometimes without affecting global gene expression levels. This promoter switch was mediated by the DDX5/DDX17 family of ERalpha coregulators. Finally, genes with DR promoters were preferentially involved in specific processes (e.g., cell structure and motility, and cell cycle). We show, in particular, that isoforms encoded by the NET1 gene APs, which are inversely regulated by estradiol, play distinct roles in cell adhesion and cell cycle regulation and that their expression is differentially associated with prognosis in ER(+) breast cancer. Altogether, this study identifies the patterns of AP regulation in ERGs and shows the contribution of AP-encoded isoforms to the estradiol-regulated transcriptome as well as their physiopathologic significance in breast cancer.
authors.affiliation: Institut National de la Sante et de la Recherche Medicale, U590, Centre Léon Bérard, Lyon, France.
authors.forename: Martin
authors.initials: M
authors.lastname: Dutertre
authors.forename: Lise
authors.initials: L
authors.lastname: Gratadou
authors.forename: Etienne
authors.initials: E
authors.lastname: Dardenne
authors.forename: Sophie
authors.initials: S
authors.lastname: Germann
authors.forename: Samaan
authors.initials: S
authors.lastname: Samaan
authors.forename: Rosette
authors.initials: R
authors.lastname: Lidereau
authors.forename: Keltouma
authors.initials: K
authors.lastname: Driouch
authors.forename: Pierre
authors.initials: P
authors.lastname: de la Grange
authors.forename: Didier
authors.initials: D
authors.lastname: Auboeuf
mesh_terms: D001943:Breast Neoplasms / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D000076246:CCCTC-Binding Factor; D045744:Cell Line, Tumor; D053487:DEAD-box RNA Helicases / Q000235:genetics; D004958:Estradiol / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism; D005091:Exons; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D000076246:CCCTC-Binding Factor; C000619697:CTCF protein, human; D047628:Estrogen Receptor alpha; D020033:Protein Isoforms; D012097:Repressor Proteins; D004958:Estradiol; C102004:DDX17 protein, human; C506749:Ddx5 protein, human; D053487:DEAD-box RNA Helicases