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Response to estradiol-ERalpha ERE Binding defective mutant

ABSTRACT: In addition to the estrogen responsive element (ERE)-dependent gene expression, E2-ERalpha regulates transcription through functional interactions with transfactors bound to their cognate regulatory elements on DNA, hence the ERE-independent signaling pathway. However, the relative importance of the ERE-independent pathway in E2-ERalpha signaling is unclear. Our studies in infected ER-negative cell models with an ERalpha mutant (ERalpha 203/204/211E) that functions exclusively at the ERE-independent pathway demonstrated that genomic responses assessed by microarrays from the ERE-independent pathway to E2-ERalpha are not sufficient to alter cellular growth, death or motility. These findings suggest that the ERE-dependent pathway is the canonical E2-ERalpha signaling in model cell lines. Keywords: MDA-MB-231 cells

ORGANISM(S): Homo sapiens

PROVIDER: GSE9758 | GEO | 2007/12/04

SECONDARY ACCESSION(S): PRJNA105107

REPOSITORIES: GEO

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Project description:Using a chromatin immunoprecipitation-paired end diTag cloning and sequencing strategy, we mapped estrogen receptor alpha (ERalpha) binding sites in MCF-7 breast cancer cells. We identified 1,234 high confidence binding clusters of which 94% are projected to be bona fide ERalpha binding regions. Only 5% of the mapped estrogen receptor binding sites are located within 5 kb upstream of the transcriptional start sites of adjacent genes, regions containing the proximal promoters, whereas vast majority of the sites are mapped to intronic or distal locations (>5 kb from 5' and 3' ends of adjacent transcript), suggesting transcriptional regulatory mechanisms over significant physical distances. Of all the identified sites, 71% harbored putative full estrogen response elements (EREs), 25% bore ERE half sites, and only 4% had no recognizable ERE sequences. Genes in the vicinity of ERalpha binding sites were enriched for regulation by estradiol in MCF-7 cells, and their expression profiles in patient samples segregate ERalpha-positive from ERalpha-negative breast tumors. The expression dynamics of the genes adjacent to ERalpha binding sites suggest a direct induction of gene expression through binding to ERE-like sequences, whereas transcriptional repression by ERalpha appears to be through indirect mechanisms. Our analysis also indicates a number of candidate transcription factor binding sites adjacent to occupied EREs at frequencies much greater than by chance, including the previously reported FOXA1 sites, and demonstrate the potential involvement of one such putative adjacent factor, Sp1, in the global regulation of ERalpha target genes. Unexpectedly, we found that only 22%-24% of the bona fide human ERalpha binding sites were overlapping conserved regions in whole genome vertebrate alignments, which suggest limited conservation of functional binding sites. Taken together, this genome-scale analysis suggests complex but definable rules governing ERalpha binding and gene regulation. Experiment Overall Design: We used oligonucleotide expression microarrays (Affymetrix GeneChip U133 Plus 2.0) to identify estradiol (E2)-responsive genes in the estrogen-receptor positive breast cancer cell line, MCF7. MCF7 cells were grown to 30-50% confluency and exposed to 10 nM E2 (or vehicle only) at 12, 24, and 48 hours. Each timepoint was performed in triplicate (ie, biological replicates). Total RNA was isolated from cells using the Qiagen RNeasy kit, and 5 micrograms of total RNA was amplified, labeled and hybridized to the array according to the manufacturerâs protocols.

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Response to estradiol-ERalpha ERE Binding defective mutant

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