Transcriptional Regulation of Estrogen Receptor (ER) by CARM1

描述（由申请人提供）：CARM1，辅助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、E2F1和类固醇受体，其中以CARM1对雌激素受体（er）的转录激活最为明显。CARM1在R17位点甲基化组蛋白H3，这种甲基化与er靶基因pS2的激活相关。CARM1的缺失导致雌激素反应的消失和一些er靶基因的表达减少。我们最近发现了一个carm1相关复合体，核小体甲基化激活因子复合体（NuMAC），它包括SWI/SNF染色质重塑复合体的多个组分。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CARM1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。我们已经生成了CARM1磷酸化缺陷突变体，这为我们研究CARM1复合物调控er信号的分子机制提供了有力的工具。本研究旨在进一步了解ER背景下CARM1的转录调控模式和细胞信号转导。鉴于人们对组蛋白精氨酸甲基化在转录调控中的作用以及内质网共激活因子复合体中两种酶活性（HMT和atp依赖性重塑）的结合兴趣的增加，我们的长期目标是分析CARM1复合体对内质网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CARM1及其相关的酶活性在调节er靶基因的一个子集中是重要的。CARM1在信号转导中发挥核心作用，信号转导受上游细胞通路调节，并编码组蛋白上的甲基标记，导致下游转录激活。在此，我概述了一系列使用生化、细胞和基因组方法研究的实验：(a) CARM1和SWI/SNF调控er靶基因表达的分子机制；(b) CARM1磷酸化对er依赖性转录和上游信号通路的影响，并导致CARM1失活；(c)雌激素依赖性组蛋白精氨酸甲基化的下游细胞效应。这些研究将为组蛋白精氨酸甲基化在内质网调控过程中的机制和功能意义提供新的认识。

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.