title: Estrogen receptor alpha inhibits p53-mediated transcriptional repression: implications for the regulation of apoptosis.
abstract: Estrogen receptor alpha (ERalpha) and tumor suppressor protein p53 exert opposing effects on cellular proliferation. As a transcriptional regulator, p53 is capable of activating or repressing various target genes. We have previously reported that ERalpha binds directly to p53, leading to down-regulation of transcriptional activation by p53. In addition to transcriptional activation, transcriptional repression of a subset of target genes by p53 plays important roles in diverse biological processes, such as apoptosis. Here, we report that ERalpha inhibits p53-mediated transcriptional repression. Chromatin immunoprecipitation assays reveal that ERalpha interacts in vivo with p53 bound to promoters of Survivin and multidrug resistance gene 1, both targets for transcriptional repression by p53. ERalpha binding to p53 leads to inhibition of p53-mediated transcriptional regulation of these genes in human cancer cells. Transcriptional derepression of Survivin by ERalpha is dependent on the p53-binding site on the Survivin promoter, consistent with our observation that p53 is necessary for ERalpha to access the promoters. Importantly, mutagenic conversion of this site to an activation element enabled ERalpha to repress p53-mediated transcriptional activation. Further, RNA interference-mediated knockdown of ERalpha resulted in reduced Survivin expression and enhanced the propensity of MCF-7 cells to undergo apoptosis in response to staurosporine treatment, an effect that was blocked by exogenous expression of Survivin. These results unravel a novel mechanism by which ERalpha opposes p53-mediated apoptosis in breast cancer cells. The findings could have translational implications in developing new therapeutic and prevention strategies against breast cancer.
authors: Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, New York 14263, USA.
authors: Aejaz
authors: A
authors: Sayeed
authors: Santhi D
authors: SD
authors: Konduri
authors: Wensheng
authors: W
authors: Liu
authors: Sanjay
authors: S
authors: Bansal
authors: Fengzhi
authors: F
authors: Li
authors: Gokul M
authors: GM
authors: Das
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001665:Binding Sites; D001859:Bone Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D015536:Down-Regulation; D050687:E2F1 Transcription Factor / Q000378:metabolism; D020847:Estrogen Receptor Modulators / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D006655:Histone Deacetylases / Q000378:metabolism; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis / Q000235:genetics; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics; D012516:Osteosarcoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D019311:Staurosporine / Q000494:pharmacology; D000077022:Survivin; D015533:Transcriptional Activation / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; C107489:BIRC5 protein, human; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D020847:Estrogen Receptor Modulators; D047628:Estrogen Receptor alpha; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D012334:RNA, Neoplasm; D000077022:Survivin; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D006655:Histone Deacetylases; D019311:Staurosporine