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Gene Regulation by Estrogen Signaling and DNA Methylation in MCF7 Breast Cancer Cells

ABSTRACT: Estrogen signaling and epigenetic modifications, in particular DNA methylation, are involved in regulation of gene expression in breast cancers. Here we investigated a potential regulatory cross-talk between these two pathways by identifying their common target genes and exploring potential underlying molecular mechanisms in human MCF7 breast cancer cells. Principal Findings: Gene expression profiling revealed that the expression of approximately 150 genes was influenced by both 17β-estradiol (E2) and a hypomethylating agent 5-aza-2’-deoxycytidine (DAC). Based on gene ontology (GO), CpG island prediction analysis and previously reported estrogen receptor (ER) binding regions, we selected six genes for further analysis (BTG3, FHL2, PMAIP1, BTG2, CDKN1A and TGFB2). GO analysis suggests that these genes are involved in intracellular signaling cascades, regulation of cell proliferation and apoptosis, while CpG island prediction of promoter regions reveals that the promoters of these genes contain at least one CpG island. Using chromatin immunoprecipitation, we show that ERα is recruited to CpG islands in promoters, but neither in an E2- nor in a DAC-dependent fashion. DAC treatment reactivates the expression of all selected genes although only the promoters of BTG3 and FHL2 genes are methylated, with E2 treatment showing no effect on the methylation status of these promoters. Conclusions: We identified a set of genes regulated by both estrogen signaling and DNA methylation. However, our data does not support a direct molecular interplay of mediators of estrogen and epigenetic signaling at promoters of regulated genes. The aim of the study was to identify genes regulated by estrogen signaling and DNA methylation, using microarray approach.

ORGANISM(S): Homo sapiens

PROVIDER: GSE36683 | GEO | 2012/12/31

SECONDARY ACCESSION(S): PRJNA153595

REPOSITORIES: GEO

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Project description:Estrogen signaling and epigenetic modifications, in particular DNA methylation, are involved in regulation of gene expression in breast cancers. Here we investigated a potential regulatory cross-talk between these two pathways by identifying their common target genes and exploring potential underlying molecular mechanisms in human MCF7 breast cancer cells. Principal Findings: Gene expression profiling revealed that the expression of approximately 150 genes was influenced by both 17β-estradiol (E2) and a hypomethylating agent 5-aza-2’-deoxycytidine (DAC). Based on gene ontology (GO), CpG island prediction analysis and previously reported estrogen receptor (ER) binding regions, we selected six genes for further analysis (BTG3, FHL2, PMAIP1, BTG2, CDKN1A and TGFB2). GO analysis suggests that these genes are involved in intracellular signaling cascades, regulation of cell proliferation and apoptosis, while CpG island prediction of promoter regions reveals that the promoters of these genes contain at least one CpG island. Using chromatin immunoprecipitation, we show that ERα is recruited to CpG islands in promoters, but neither in an E2- nor in a DAC-dependent fashion. DAC treatment reactivates the expression of all selected genes although only the promoters of BTG3 and FHL2 genes are methylated, with E2 treatment showing no effect on the methylation status of these promoters. Conclusions: We identified a set of genes regulated by both estrogen signaling and DNA methylation. However, our data does not support a direct molecular interplay of mediators of estrogen and epigenetic signaling at promoters of regulated genes. The aim of the study was to identify genes regulated by estrogen signaling and DNA methylation, using microarray approach. We compared the effects of E2 and DAC on global gene expression profiles in MCF7 cells. By comparing C_E2 (MP5-MP8 average) with C_EtOh samples (MP1-MP4 average), 802 genes were identified as up-regulated by E2, while 851 genes were identified as down-regulated by E2. 1017 genes were identified as up-regulated by DAC, by comparing A_EtOh (MP9-MP12 average) samples with C_EtOh, suggesting that DNA methylation is involved in their regulation. To identify possible common targets, we have compared the DAC up-regulated genes with E2-regulated genes. 88 annotated genes are found to be up-regulated by both E2 and DAC, suggesting that E2 has a hypomethylation-like effect on the regulation of these genes. 58 annotated genes are found to be down-regulated by E2 and up-regulated by DAC, suggesting that E2 has a hypermethylation-like effect on the regulation of these genes.

Project description:Multiple signaling pathways ultimately modulate the epigenetic information embedded in the chromatin of gene promoters by recruiting epigenetic enzymes. We found that, in estrogen-regulated gene programming, the acetyltransferase CREB-binding protein (CBP) is specifically and exclusively methylated by the coactivator-associated arginine methyltransferase (CARM1) in vivo. CARM1-dependent CBP methylation and p160 coactivators were required for estrogen-induced recruitment to chromatin targets. Notably, methylation increased the histone acetyltransferase (HAT) activity of CBP and stimulated its autoacetylation. Comparative genome-wide chromatin immunoprecipitation sequencing (ChIP-seq) studies revealed a variety of patterns by which p160, CBP, and methyl-CBP (meCBP) are recruited (or not) by estrogen to chromatin targets. Moreover, significant target gene-specific variation in the recruitment of (1) the p160 RAC3 protein, (2) the fraction of a given meCBP species within the total CBP, and (3) the relative recruitment of different meCBP species suggests the existence of a target gene-specific âfingerprintâ for coregulator recruitment. Crossing ChIP-seq and transcriptomics profiles revealed the existence of meCBP âhubsâ within the network of estrogen-regulated genes. Together, our data provide evidence for an unprecedented mechanism by which CARM1-dependent CBP methylation results in gene-selective association of estrogen-recruited meCBP species with different HAT activities and specifies distinct target gene hubs, thus diversifying estrogen receptor programming. Examination of estrogen-induced binding site in H3396 cells under Estrogen (E2) or Ethanol (EtOH) treatment: CBP in E2; CBP in EtOH (two technical replicate); CBPR742m in E2 (two technical replicates); CBPR768m in E2; CBPR768m in EtOH; CBPR2151m in E2; CBPR2151m in EtOH; Estrogen receptor alpha (ERa) in E2; ERa in EtOH; Total Histone 3 and 4 acetylated in E2; H3K18ac in E2; H3K18ac in EtOH; Polymerase II (PolII) in E2; PolII in EtOH; RAC3 in E2; Input DNA sample in E2

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Gene Regulation by Estrogen Signaling and DNA Methylation in MCF7 Breast Cancer Cells

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