Transcriptional Regulation of Estrogen Receptor (ER) by CARM1

描述（由申请人提供）：CARM 1，辅激活因子相关精氨酸（R）甲基转移酶1，参与许多转录因子的激活，包括NF-？B、p53、E2 F1和类固醇受体，其中通过CARM 1的雌激素受体（ER）的转录激活被最好地表征。CARM 1在R17处甲基化组蛋白H3，并且这种甲基化与ER靶基因pS2的激活相关。CARM 1的缺失导致雌激素反应的消除和一些ER靶基因表达的减少。我们最近发现了一个CARM 1相关的复合物，核小体甲基化激活剂复合物（NuMAC），其中包括SWI/SNF染色质重塑复合物的多个组件。SWI/SNF也与ER介导的转录激活有关，SWI/SNF功能的丧失在癌症进展中很常见。有趣的是，我们最近发现CARM 1可以在体内磷酸化，并且其磷酸化抑制其组蛋白甲基转移酶（HMT）活性。我们已经产生了磷酸化缺陷突变体的CARM 1，这为我们提供了一个强大的工具，以调查的ER-signaling的调控的分子机制的CARM 1复合物。本研究旨在进一步了解CARM 1在ER背景下的转录调控模式和细胞信号传导。鉴于组蛋白精氨酸甲基化在转录调控中的兴趣激增，以及在ER共激活因子复合物中掺入两种酶活性（HMT和ATP依赖性重塑），我们的长期目标是分析CARM 1复合物对ER转录调控的分子基础，并确定其与乳腺癌发展的功能相关性。我们的中心假设是，CARM 1及其相关的酶活性在调节ER靶基因的子集中是重要的。CARM 1在信号转导中起着核心作用，其受上游细胞通路的调节，并编码组蛋白上的甲基标记以导致下游转录激活。在这里，我概述了一系列的实验，使用生物化学，细胞为基础的，和基因组的方法来研究：（a）的ER靶基因表达的调控的分子机制，由CARM 1和SWI/SNF;（B）的影响，CARM 1磷酸化ER依赖性转录和上游信号通路，并导致CARM 1失活;和（c）雌激素依赖性组蛋白精氨酸甲基化的下游细胞效应。这些研究将为深入了解组蛋白精氨酸甲基化在内质网调控过程中的作用机制和功能意义提供新的思路。

DESCRIPTION (provided by applicant): CARM1, coactivator associated arginine (R) methyltransferase 1, is involved in the activation of a number of transcriptional factors, including NF-?B, p53, E2F1 and steroid receptors, among which transcriptional activation of estrogen receptors (ERs) by CARM1 is best characterized. CARM1 methylates histone H3 at R17, and this methylation correlates with activation of the ER-target gene pS2. Loss of CARM1 leads to abrogation of the estrogen response and reduction in expression of some ER-target genes. We recently identified a CARM1-associated complex, nucleosomal methylation activator complex (NuMAC), which includes multiple components of SWI/SNF chromatin remodeling complex. SWI/SNF has also been implicated in ER-mediated transcriptional activation, and loss of SWI/SNF function is common in cancer progression. Interestingly, we have recently found that CARM1 can be phosphorylated in vivo and that its phosphorylation inhibits its histone methyltransferase (HMT) activity. We have generated phosphorylation-defective mutants of CARM1, which provide us a powerful tool to investigate the molecular mechanism of the regulation of ER-signaling by the CARM1 complex. This study is proposed to further understand the mode of transcriptional regulation and the cellular signaling of CARM1 in the context of ER. Given the surge of interest in histone arginine methylation in transcriptional regulation and the incorporation of two enzymatic activities, HMT and ATP-dependent remodeling, in the ER coactivator complex, our long-term objectives are to analyze the molecular underpinnings of ER transcriptional regulation by the CARM1 complex and to determine its functional relevance to the development of breast cancer. Our central hypothesis is that CARM1 and its associated enzymatic activities are important in regulating a subset of ER-target genes. CARM1 plays a central role in signal transduction, which is regulated by upstream cellular pathways and encodes a methyl-mark on histones to lead to the downstream transcription activation. Here I outline a series of experiments using biochemical, cell-based, and genomic approaches to study: (a) the molecular mechanism of the regulation of ER-target gene expression by CARM1 and SWI/SNF; (b) the effect of CARM1 phosphorylation on ER-dependent transcription and upstream signaling pathways and that lead to CARM1 inactivation; and (c) the downstream cellular effects of estrogen-dependent histone arginine methylation. These studies will provide a new understanding of the mechanism and functional significance of histone arginine methylation in ER-regulated processes.