Regulatory Mechanisms in Transcriptional Signaling

描述(由申请人提供)：转录调控在确定细胞和组织分化、细胞生长、发育和疾病易感性方面起着重要作用。真核基因表达的高度调控过程是由染色质、核激素受体等转录因子和具有组蛋白/染色质修饰活性的关键辅助/调节蛋白等多种机制相互作用而协调的。组蛋白经过翻译后修饰，如乙酰化、磷酸化和甲基化。这些修饰的组蛋白随后导致了转录的“组蛋白密码”的建立。例如，未修饰的组蛋白抑制转录，而乙酰化的历史促进基因激活。在高等真核生物中，未修饰的组蛋白“编码”转录抑制的机制在很大程度上是未知的。辅调节因子的翻译后修饰也会影响基因转录。我们研究的长期目标是识别和分子表征调节激素信号和转录的新机制。我们最近发现，一种名为INHAT的人类细胞复合体至少部分通过与组蛋白结合并调节组蛋白乙酰转移酶的活性来调节核受体的功能和转录。pp32是INHAT复合体的一个亚单位，也是一种核磷蛋白。我们假设pp32是转录抑制的关键成分，pp32的磷酸化在其体内功能中起着关键作用。为了验证这些假说，我们将(1)确定pp32在转录抑制性“组蛋白密码”翻译中的作用；(2)表征pp32转录抑制的分子机制；(3)分析磷酸化在pp32体内功能中的作用。我们将结合使用生化、分子和细胞生物学方法的体外和体内分析来解决上述具体目标。调节组蛋白修饰和蛋白磷酸化的蛋白质活性改变与激素信号改变以及包括癌症和发育异常在内的人类疾病有关。来自拟议研究的信息不仅应该提供对转录和激素信号的更好理解，而且还可能在治疗人类疾病的靶向药物开发中有用。

DESCRIPTION (provided by applicant): Transcriptional regulation plays a fundamental role in specifying cellular and tissue differentiation, cell growth, development and susceptibility to diseases. The highly regulated process of eukaryotic gene expression is coordinated by the interplay of multiple mechanisms involving chromatin, transcription factors such as nuclear hormone receptors and critical accessory/regulatory proteins with histone/chromatin modifying activities. Histones undergo posttranslational modifications such as acetylation, phosphorylation and methylation. These modified histones subsequently led to the establishment of a "histone code" of transcription. For example, unmodified histones repress transcription while acetylated histories promote gene activation. The mechanisms by which unmodified histones "code" for transcriptional repression in higher eukaryotes are largely unknown. Post-translational modification of coregulators also influence gene transcription. The long-term goal of our research is to identify and molecularly characterize novel mechanisms regulating hormonal signaling and transcription. We have recently shown that a human cellular complex termed INHAT regulates nuclear receptor function and transcription at least in part by binding to histones and modulating histone acetyltransferase activity of coactivators, pp32 is a subunit of the INHAT complex and a nuclear phosphoprotein. We hypothesize that pp32 is a critical component in transcriptional repression and that phosphorylation of pp32 plays a critical role in its in vivo function. To test the hypotheses we will (1) determine the role ofpp32 in translating the repressive "histone code" of transcription; (2) characterize molecular mechanisms of transcriptional repression by pp32; and (3) analyze the role of phosphorylation in pp32 function in vivo. We will address the above specific aims using a combination of in vitro and in vivo analyses involving biochemical, molecular, and cell biological methodologies. Altered activities of proteins regulating histone modifications and protein phosphorylation have been linked to altered hormone signaling and human diseases including cancer, and developmental abnormalities. The information stemming from the proposed studies should not only provide a better understanding of transcription and hormone signaling but may also be useful in targeted drug development to treat human diseases.