MECHANISM OF ACTIVATION BY NUCLEAR RECEPTOR COACTIVATORS

类固醇-甲状腺激素受体(或核受体)超家族 包括类固醇、甲状腺、维生素A和维生素D受体。 这些受体及其相关信号通路的缺陷 与许多遗传性疾病有关，类固醇受体 在乳腺癌、前列腺癌和前列腺癌的病因和治疗中的重要作用 淋巴癌。这些激素控制转录激活剂 结合到与它们的基因关联的特定增强子元件 调节并从而促进功能物质的组装或激活 转录起始前复合体。转录激活通过 核受体是由一个新的三种蛋白质家族介导的。 核受体辅活化子(NRCoA)；三个150-160 kDa 蛋白质有SRC-1、GRIP1或TIF2和p/CIP(它也有几个 其他名称)。这些蛋白质的功能结构域仍不清楚。 调查，但包括位于中心的NR相互作用域；一个 包含结合位点的转录激活结构域 辅活化子CBP或p300；第二转录激活结构域 不依赖CBP的C末端；以及组蛋白乙酰转移酶 (HAT)C-末端结构域的活性。人们对此知之甚少 这些NRCoA介导转录激活的机制 美国国税局。我们的工作假设是，病毒的C-末端区域 NRCoA，它包含反式激活和HAT活性，以及N- 末端区域，这是 三个NRCoA，在辅活化子活性中发挥重要作用 与转录机制中的蛋白质直接或间接接触 和/或染色质。我们最近开发了一系列瞬变的 证实NRCoA共激活功能的转染实验 在哺乳动物细胞中；在这些检测中，N-末端或 C-末端结构域显著改变了NRCoA的功能。这里 我们建议详细映射与这些相关的子域 活性，并鉴定和表征特定的细胞蛋白 与这些域相关联并协调它们的活动。这个 NRCoA代表了NR信号通路激活的新步骤 对特定激素作出反应的特定基因的转录。这个 拟议的调查将确定这条途径的下一步(S)。 长期目标是完全定义蛋白质成分， 将激活的、DNA结合的NRS的激活信号传输到 转录机器。

The steroid-thyroid hormone receptor (or nuclear receptor) superfamily includes the steroid, thyroid, vitamin A, and vitamin D receptors. Deficiencies in these receptors and their associated signaling pathways are associated with many genetic diseases, and steroid receptors have important roles in the etiology and treatment of breast, prostate, and lymphoid cancers. These hormone controlled transcriptional activators bind to specific enhancer elements assoicated with the genes they regulate and thereby promote the assembly or activation of a functional transcription pre-initiation complex. Transcriptional activation by nuclear receptors (NR) is mediated by a new family of three proteins, the Nuclear Receptor Coactivators (NRCoA); the three 150-160-kDa proteins are SRC-1; GRIP1 or TIF2; and p/CIP (which also has several other names). The functional domains of these proteins are still under investigation but include a centrally located NR interaction domain; one transcriptional activation domain that contains a binding site for the coactivator CBP or p300; a second transcriptional activation domain near the C-terminus that is CBP-independent; and a histone acetyltransferase (HAT) activity in the C-terminal domain. Little is known about the mechanism by which these NRCoAs mediate transcriptional activation of NRs. Our working hypothesis is that the C-terminal region of the NRCoAs, which contains transactivation and HAT activities, and the N- terminal region, which is the most highly conserved region among the three NRCoAs, play important roles in coactivator activity by making direct or indirect contact with proteins in the transcription machinery and/or chromatin. We have recently developed a series of transient transfection assays that demonstrate the coactivator function of NRCoAs in mammalian cells; in these assays deletion of the N-terminal or the C-terminal domain dramatically alters the function of the NRCoAs. Here we propose to map in detail the subdomains associated with these activities and to identify and characterize specific cellular proteins that associate with these domains and mediate their activities. The NRCoAs represent a new step in the NR signaling pathways that activate transcription of specific genes in response to specific hormones. The proposed investigations will identify the next step(s) in the pathway. The long range goal is to completely define the protein components that transmit the activating signal from the activated, DNA-bound NRs to the transcription machinery.