MHC Class II Transactivator Function and Regulation

描述（由申请人提供）：MHC II类基因的适当和正常调节对健康和活跃的免疫系统至关重要，对我们对抗病原体的能力至关重要。II类反式激活因子CIITA是MHC-II基因表达的主要调节因子。尽管对CIITA进行了广泛的分析，但CIITA生物学的重要方面以及因此MHC-II调节仍然未知。该提案将侧重于CIITA的结构、监管和功能三个方面。CIITA自我关联，这是一个对其功能至关重要的特性，但寡聚化如何有助于CIITA激活MHC-II基因的能力尚不清楚。在目标1中，我们将测试的假设，寡聚化有助于CIITA的能力，以结合其目标蛋白的MHC-II启动子，相互作用和控制染色质重塑，和/或用于连接调节元件。第二个目的是确定CIITA基因沉默的机制，发生在生殖中心B细胞分化为浆细胞。我们的数据表明，基因沉默发生在局部染色质结构的水平，并介导的特定组蛋白修饰的变化。重要的是，已经鉴定了一组全局阻遏物（Blimp-1）和共阻遏物（MTA-3和BCL-6），它们分别介导向浆细胞的转变或B细胞程序的维持。沿着细胞培养系统，这些阻遏物将用于异位控制CIITA沉默和表达，从而可以阐明染色质控制的分子机制。因此，CIITA将作为这一重要细胞命运决定的模型。最后，在DC和巨噬细胞中，CIITA从四个启动子中的第一个（pl）转录。 该转录物（pl-CIITA）编码具有增强的转录活性的独特同种型，但该同种型的确切功能和该DC/巨噬细胞特异性启动子的具体作用是未知的。在目标3中，我们将创建小鼠来检查该启动子及其同种型在发展和启动免疫应答中发挥的新作用。由于DC/巨噬细胞提供了对病原体的前线防御，因此该模型系统将为该启动子和同种型提供明确的作用。因此，本申请的中心目标是充分理解CIITA发挥作用以调节MHC-II基因系统的分子机制。这些研究的结果将最终确定感染性疾病、自身免疫性疾病和器官移植的免疫治疗靶点。

DESCRIPTION (provided by applicant): The appropriate and normal regulation of MHC class II genes is central to a healthy and active immune system and critical for our ability to combat pathogens. The class II transactivator, CIITA, is the master regulator of MHC-II gene expression. Despite extensive analysis of CIITA important aspects of CIITA biology and therefore MHC-II regulation remain unknown. This proposal will focus on three aspects of CIITA structure, regulation, and function. CIITA self-associates, a property that is critical to its function, but how oligomerization contributes to CIITA's ability to activate MHC-II genes is not known. In Aim 1, we will test the hypothesis that oligomerization contributes to the ability of CIITA to bind to its target proteins on MHC-II promoters, interact and control chromatin remodeling, and/or serve to link regulatory elements. The second aim seeks to determine the mechanism of CIITA gene silencing that occurs as germinal center B cells differentiate into plasma cells. Our data indicate that gene silencing occurs at the level of the local chromatin structure and is mediated by changes in specific histone modifications. Importantly, a set of global repressers (Blimp-1) and co-repressors (MTA-3 and BCL-6) has been identified that mediate the transition to plasma cells or the maintenance of the B cell program, respectively. Along with cell culture systems, these repressers will be used to ectopically control CIITA silencing and expression such that the molecular mechanism of chromatin control can be elucidated. CIITA will therefore serve as a model for this important cell fate decision. Lastly, in DC and macrophages CIITA is transcribed from the first (pl) of four promoters. This transcript (pl-CIITA) encodes a unique isoform with enhanced transcriptional activity, yet the exact function of this isoform and the specific role of this DC/macrophage specific promoter are unknown. In Aim 3, we will create mice to examine the novel role that this promoter and its isoform play in developing and initiating immune responses. Because DC/macrophages provide the front line defense to pathogens, this model system will provide a clear role for this promoter and isoform. Thus, the central goal of this application is to understand fully the molecular mechanisms by which CIITA functions to regulate the MHC-II gene system. The results of these studies will ultimately identify targets for immune based therapies for the infectious disease, autoimmune disorders, and organ transplantation.