Project description:We are studying the mechanisms by which the estrogen receptor, ERalpha, is recruited to and regulates genes with a non-direct DNA binding. We performed ChIP-chip for ERalpha in E2 treated HeLa-ER cells, and looked at 19000 RefSeq genes to determine binding patterns of the receptor at promoters. The experiment was performed in duplicate.
Project description:In breast cancer and normal estrogen target tissues, estrogen receptor alpha (ERalpha) signaling results in establishment of spatiotemporal patterns of gene expression. A time-course series of ChIP-chip experiments were performed to identify direct ERalpha target genes and determine whether these targets were transcriptionally activated or repressed by ERalpha. Keywords: Time-course ChIP-chip
Project description:Estrogen plays an important role in the regulation of vascular tone and in the pathophysiology of cardiovascular disease. Physiological effects of estrogen are mediated through estrogen receptors alpha (ERalpha) and beta (ERbeta), which are both expressed in vascular smooth muscle and endothelial cells. However, the molecular pathways mediating estrogen effects in blood vessels are not well defined. We have performed gene expression profiling in the mouse aorta to identify comprehensive gene sets the expression of which is regulated by long-term (1 wk) estrogen treatment. The ER subtype dependence of the alterations in gene expression was characterized by parallel gene expression profiling experiments in ERalpha-deficient [ERalpha knockout (ERalphaKO)] and ERbeta-deficient (ERbetaKO) mice. Importantly, these data revealed that ERalpha- and ERbeta-dependent pathways regulate distinct and largely nonoverlapping sets of genes. Whereas ERalpha is essential for most of the estrogen-mediated increase in gene expression in wild-type aortas, ERbeta mediates the large majority of estrogen-mediated decreases in gene expression. Biological functions of the estrogen-regulated genes include extracellular matrix synthesis, in addition to electron transport in the mitochondrion and reactive oxygen species pathways. Of note, the estrogen/ERbeta pathway mediates down-regulation of mRNAs for nuclear-encoded subunits in each of the major complexes of the mitochondrial respiratory chain. Several estrogen-regulated genes also encode transcription factors. Overall, these findings provide a foundation for understanding the molecular basis for estrogen effects on vasculature gene expression. Keywords: estrogen, estrogen receptor knockout, gene expression, mouse aorta
Project description:We are studying the mechanisms by which the estrogen receptor, ERalpha, is recruited to and regulates genes with a non-direct DNA binding. We performed ChIP-chip for ERalpha in E2 treated HeLa-ER cells, and looked at 19000 RefSeq genes to determine binding patterns of the receptor at promoters. The experiment was performed in duplicate. ChIP-chip biological replicates for Eralpha in E2 treated HeLa-ER cells are included.
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. Keywords: time course
Project description:Estrogen receptor alpha (ERalpha signaling pathway is essential for ERalpha positive breast cancer progression and endocrine therapy resistance. BPTF associated protein of 18kDa (BAP18) has been recognized as a crucial H3K4me3 reader. However, the whole genomic occupation of BAP18 and its biological function in breast cancer are still elusive. Here, we found that higher expression of BAP18 in ERalpha positive breast cancer is positively correlated with poor prognosis. ChIP-seq analysis further demonstrated that the half estrogen response elements (EREs) and the CCCTC binding factor (CTCF) binding sites are the significant enrichment sites found in estrogen-induced BAP18 binding sites. In addition, we provide the evidence to demonstrate that BAP18 as a novel co-activator of ERalpha is required for the recruitment of COMPASS-like core subunits to cis-regulatory element of ERalpha target genes in breast cancer cells. BAP18 is recruited to the promoter regions of estrogen-induced genes, accompanied with the enrichment of the lysine 4-trimethylated histone H3 tail (H3K4me3) in the presence of E2. Furthermore, BAP18 promotes cell growth and confers to ERalpha antagonist tamoxifen resistancein ERalpha positive breast cancer. Our data suggest that BAP18 facilitates the association between ERalpha and COMPASS-like core subunits, which might be an essential epigenetic therapeutic target for breast cancer.
Project description:Two subtypes of the estrogen receptor, ERalpha and ERbeta, mediate the actions of estrogens, and the majority of human breast tumors contain both ERalpha and ERbeta. To examine the possible interactions and modulatory effects of ERbeta on ERalpha activity, we have used adenoviral gene delivery to produce human breast cancer (MCF-7) cells expressing ERbeta, along with their endogenous ERalpha. We have examined the effects of ERβ expression on genome-wide gene expression by Affymetrix GeneChip microarrays. We find that ERbeta modulated estrogen gene expression on nearly 24% of E2-stimulated genes but only 8% of E2-inhibited genes. We find that ERbeta modulation is gene-specific, enhancing or counteracting ERalpha regulation for distinct subsets of estrogen target genes. Introduction of ERbeta into ERalpha-containing cells induced up/down-regulation of many estrogen target in the absence of any added ligand. In addition, ERbeta presence elicited the expression of a unique set of genes that were not regulated by ERalpha alone. ERbeta modulated the expression of genes in many functional categories, but the greatest numbers were associated with transcription factor and signal transduction pathways. Regulation of multiple components in the TGF beta, SDF1, and semaphorin pathways, may contribute to the suppression of proliferation observed with ERbeta both in the presence and absence of estrogen. Hence, ERbeta modulates ERalpha gene regulation in diverse ways that may contribute to its growth-inhibiting beneficial effects in breast cancer Keywords: modulatory effects of ERb on ERa
Project description:To explore the global mechanisms of estrogen-regulated transcription, we used chromatin immunoprecipitation coupled with DNA microarrays to determine the localization of RNA polymerase II (Pol II), estrogen receptor alpha (ERalpha), steroid receptor coactivator proteins (SRC), and acetylated histones H3/H4 (AcH) at estrogen-regulated promoters in MCF-7 cells with or without estradiol (E2) treatment. In addition, we correlated factor occupancy with gene expression and the presence of transcription factor binding elements. Using this integrative approach, we defined a set of 58 direct E2 target genes based on E2-regulated Pol II occupancy and classified their promoters based on factor binding, histone modification, and transcriptional output. Many of these direct E2 target genes exhibit interesting modes of regulation and biological activities, some of which may be relevant to the onset and proliferation of breast cancers. Our studies indicate that about one-third of these direct E2 target genes contain promoter-proximal ERalpha-binding sites, which is considerably more than previous estimates. Some of these genes represent possible novel targets for regulation through the ERalpha/AP-1 tethering pathway. Our studies have also revealed several previously uncharacterized global features of E2-regulated gene expression, including strong positive correlations between Pol II occupancy and AcH levels, as well as between the E2-dependent recruitment of ERalpha and SRC at the promoters of E2-stimulated genes. Furthermore, our studies have revealed new mechanistic insights into E2-regulated gene expression, including the absence of SRC binding at E2-repressed genes and the presence of constitutively bound, promoter-proximally paused Pol IIs at some E2-regulated promoters. These mechanistic insights are likely to be relevant for understanding gene regulation by a wide variety of nuclear receptors. Keywords: MCF7 cells, E2, Estrogen, RNA, ER, RNA Polymerase II, SRC, Acetylated histones, ChIP-chip
Project description:Estrogen has vascular protective effects in premenopausal women and in women under 60 receiving hormone replacement therapy. However, estrogen also increases risks of breast and uterine cancers and of venous thromboses linked to upregulation of coagulation factors in the liver. In mouse models, the vasoprotective effects of estrogen are mediated by the estrogen receptor alpha (ERa) transcription factor. Here, through next generation sequencing approaches, we show that almost all of the genes regulated by 17-b-estradiol (E2) differ between mouse aorta and mouse liver, and that this is associated with a distinct genomewide distribution of ERa on chromatin. Bioinformatic analysis of E2-regulated promoters and ERa binding site sequences identify several transcription factors that may determine the tissue specificity of ERa binding and E2-regulated genes, including the enrichment of NFkB, AML1 and AP-1 sites in the promoters of E2 downregulated inflammatory genes in aorta but not liver. The possible vascular-specific functions of these factors suggests ways in which the protective effects of estrogen could be promoted in the vasculature without incurring negative effects in other tissues. Our results also highlight the likely importance of rapid signaling of membrane-associated ERa to cellular kinases (altering the activities of transcription factors other than ER itself) in determining tissue specific transcriptional responses to estrogen. The aortas or liver fragments of wild-type C57/BL6 mice were incubated ex vivo with 10nM E2 or ethanol vehicle for 45 minutes before formaldehyde fixation, harvesting of chromatin & ChIP with anti- mouse estrogen receptor alpha antibodies. Each condition was performed with two biological replicates, and each replicate contained aortas or liver fragments from 5 mice.