Estrogen Receptor-Coregulator Functional Interactions

细胞环境是受体-配体复合物激活转录能力的关键决定因素。可以定义ER α转录活性的因素包括辅激活因子和辅阻遏因子、受体与细胞特异性因子相互作用的相对能力、信号转导途径的变化或用于调节ER α活性的辅激活因子/辅阻遏因子的改变。本申请中概述的研究将提供关于在各种ER α靶基因上使用辅激活子和辅阻遏子的重要信息，并评估细胞信号传导途径作为配体激活ER α的贡献者的作用。 我们计划的研究基于四个关键观察。 首先，辅激活因子有助于ER α与4 HT配体的转录活性，在这种情况下，选择性雌激素受体调节剂（SERM）是一种部分激动剂。 其次，SMRT和NCoR对于4 HT的拮抗活性是重要的。第三，细胞内信号转导途径影响ER α、辅激活因子和辅抑制因子的转录活性。 最后，细胞内信号传导途径的改变伴随着细胞对部分激动剂/拮抗剂如4 HT的反应的变化。 这些观察结果导致了这样的假设，即SERM，4 HT，调节ER α依赖性生物事件的能力是通过在给定环境中与ER α功能性相互作用的辅激活子和辅抑制子的能力来调节的，并且这是通过这些分子的表达和调节它们与受体结合的能力的基因特异性和细胞特异性因子的影响来调节的。 将在以下特定目的中检验该假设：1）确定SRC家族辅激活因子对E2和4 HT调节ER α依赖性基因表达的能力的贡献; 2）确定辅阻遏因子SMRT和NCoR对E2和4 HT调节ER α依赖性基因表达的能力的贡献; 3）确定细胞环境是否影响CBP、SRC家族成员和辅阻遏物SMRT和NCoR的能力，在激素不存在或存在E2或4 HT的情况下与ER α相互作用，和4）确定雌激素-依赖性和他莫昔芬抗性乳腺癌细胞影响这些途径改变ER α和辅激活子或辅阻遏子之间的相互作用以及ER α依赖性基因表达的能力。 因此，我们的研究将提供有关4 HT以基因或细胞特异性方式调节ER α活性的能力的机制信息。

Cell environment is a critical determinant of the ability of receptor-ligand complexes to activate transcription. Factors that can define ERalpha transcriptional activity include coactivators and corepressors, the relative ability of receptors to interact with cell-specific factors, changes in signal transduction pathways, or alterations in the coactivators/corepressors utilized to regulate ERalpha activity. The studies outlined in this application will provide important information on coactivator and corepressor usage at various ERalpha target genes, and assess the role of cell signaling pathways as a contributor to ERalpha activation by ligands. Our planned studies are based on four key observations. First, coactivators contribute to the transcriptional activity of ERalpha liganded with 4HT in contexts where this selective estrogen receptor modulator (SERM) is a partial agonist. Second, SMRT and NCoR are important for the antagonistic activity of 4HT. Third, intracellular signal transduction pathways affect the transcriptional activity of ERalpha, coactivators and corepressors. Lastly, alterations in intracellular signaling pathways accompany changes in cellular responses to partial agonists/antagonists such as 4HT. These observations have lead to the hypothesis that the ability of the SERM, 4HT, to regulate ERalpha-dependent biological events is modulated by the ability of coactivators and corepressors to functionally interact with the ERalpha within a given context, and that this is regulated by the expression of these molecules and the influence of gene- specific and cell-specific factors that regulate their ability to bind to receptor. This hypothesis will be tested in the following specific aims: 1) Determine SRC family coactivators' contribution to the ability of E2 and 4HT to regulate ERalpha- dependent gene expression; 2) Determine the contribution of the corepressors, SMRT and NCoR, to the ability of E2 and 4HT to regulate ERalpha-dependent gene expression; 3) Determine whether cellular environments influence the ability of CBP, SRC family members, and the corepressors, SMRT and NCoR, to interact with ERalpha in the absence of hormone or in the presence of E2 or 4HT and 4) Determine whether changes in intracellular signaling between estrogen-dependent and tamoxifen resistant breast cancer cells affect the ability of these pathways to alter interactions between ERalpha and coactivators or corepressors, and ERalpha- dependent gene expression. Our studies will therefore provide mechanistic information on 4HT's ability to modulate ERalpha activity in a gene or cell specific manner.