ESTROGEN RECEPTOR-COREGULATOR FUNCTIONAL INTERACTIONS

描述（申请人提供）：经典雌激素受体ERα是一种配体调节的转录因子，对正常发育、体内平衡和生殖很重要，因此，了解该受体活性的正常和药理调节对人类健康具有重要意义。人们普遍认为，ERα调节基因表达的能力依赖于配体结合受体招募到其靶基因的转录共调节剂。维甲酸和甲状腺激素受体（SMRT）共调节剂的沉默介质最初被定性为ERα与选择性雌激素受体调节剂（SERM） 4-羟他莫昔芬（4HT）结合的共抑制因子，然而，它可以刺激ERα与雌二醇（E2）结合的活性，这表明SMRT是ERα的双重共激活因子/共抑制因子。最近的研究表明，SMRT与ERα相互作用的性质取决于受体是与激动剂还是拮抗剂结合。此外，除了SMRT激活组蛋白去乙酰化酶3 （HDAC3）外，该共调节因子还可以结合组蛋白去甲基化酶，从而促进ERα的转录活性。这项工作的总体目标是确定两种SMRT相互作用蛋白的能力，分别具有激活和抑制活性，以调节er α依赖基因的表达。计划中的实验将使用最先进的生物学、胞质学和转录组学分析来测试smrt - er - α相互作用性质的差异是否有助于这些不同复合物以配体和基因依赖的方式结合和/或调节er - α的能力，以及抑制复合物的组成或活性是否可以通过细胞途径调节。利用维持类固醇反应性的乳腺上皮细胞的新型三维培养和能够精确评估SMRT体内HDAC3激活活性的小鼠模型，SMRT调节ERα转录活性和乳腺发育的能力将确定SMRT在生理环境中调节ERα对激动剂和拮抗剂反应的生物学重要性。总之，这些计划中的研究将评估SMRT招募到ERα靶基因的蛋白质差异是该共调节因子对ERα依赖性基因表达影响的关键决定因素这一假设。因此，这项工作将为SMRT独立于HDAC3的作用机制，以及SMRT在雌激素依赖性疾病（如乳腺癌）中对ERα调节的贡献提供重要的见解。

DESCRIPTION (provided by applicant): The classical estrogen receptor, ERα, is a ligand-regulated transcription factor important for normal development, homeostasis and reproduction, and consequently, understanding normal and pharmacological regulation of this receptor's activity is of major significance to human health. It is well accepted that the ability of ERα to regulate gene expression is dependent upon the transcriptional coregulators that ligand-bound receptors recruit to their target genes. The silencing mediator of retinoic acid and thyroid hormone receptors (SMRT) coregulator was initially characterized as a corepressor for ERα bound to the selective estrogen receptor modulator (SERM), 4-hydroxytamoxifen (4HT), however, it can stimulate the activity of ERα bound to estradiol (E2) and this established SMRT as a dual coactivator/corepressor for ERα. Recent work demonstrates that the nature of SMRT interactions with ERα depend upon whether the receptor is bound to agonist or antagonist. Moreover, in addition to the well described activation of histone deacetylase 3 (HDAC3) by SMRT, this coregulator can also bind to a histone demethylase that promotes the transcriptional activity of ERα. The overall goal of the proposed work is to define the ability of two SMRT interacting proteins, with activating and repressive activities, respectively, to regulate ERα-dependent gene expression. The planned experiments will use state-of-the-art biological, cistromic and transcriptomic analysis to test whether differences in the nature of SMRT-ERα interactions contributes to the ability of these distinct complexes to bind and/or regulate ERα in a ligand- and gene-dependent manner, and whether the composition or activity of the repressive complexes can be regulated by cellular pathways. Using novel 3-dimensional culture of mammary epithelial cells that maintain steroid responsiveness and mouse models that enable the precise evaluation of the HDAC3 activation activity of SMRT in vivo, the ability of SMRT to regulate ERα transcriptional activity as well as mammary gland development will define the biological importance of SMRT for regulation of ERα responses to both agonists and antagonists in a physiological setting. Together, these planned studies will evaluate the hypothesis that differences in the proteins that SMRT recruits to ERα target genes are critical determinants of the effect of this coregulator on ERα-dependent gene expression. In so doing, the proposed work will provide critical insight into mechanisms of action of SMRT independent of HDAC3, and the contribution of SMRT to ERα regulation in estrogen-dependent disease such as breast cancer.