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是健康和活跃的免疫系统的核心，对我们对抗病原体的能力至关重要。第二类反式激活因子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MHC-II的调控仍然未知。这项建议将集中在CIITA的结构、监管和功能三个方面。CIITA自结合，这是其功能的关键属性，但寡聚如何有助于CIITA激活MHC-II基因的能力尚不清楚。在目标1中，我们将检验这一假设，即寡聚有助于CIITA与其在MHC-II启动子上的目标蛋白结合的能力，相互作用和控制染色质重塑，和/或起连接调控元件的作用。第二个目的是确定生发中心B细胞分化为浆细胞时CIITA基因沉默的机制。我们的数据表明，基因沉默发生在局部染色质结构的水平上，并通过特定的组蛋白修饰的变化来调节。重要的是，已经确定了一组全局抑制因子(Blimp-1)和辅助抑制因子(MTA-3和BCL-6)，它们分别介导向浆细胞的转变或维持B细胞程序。与细胞培养系统一起，这些抑制物将被用来异位控制CIITA的沉默和表达，以便阐明染色质控制的分子机制。因此，CIITA将成为这一重要细胞命运决定的典范。最后，在DC和巨噬细胞中，CIITA从四个启动子中的第一个(P1)转录而来。 该转录本(pl-CIITA)编码一种独特的具有增强转录活性的异构体，但该异构体的确切功能和该DC/巨噬细胞特异性启动子的具体作用尚不清楚。在目标3中，我们将建立小鼠来研究这种启动子及其异构体在发展和启动免疫反应中所扮演的新角色。由于DC/巨噬细胞为病原体提供了一线防御，该模型系统将为该启动子和异构体提供明确的作用。因此，这项应用的中心目标是充分了解CIITA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基于免疫的治疗传染病、自身免疫性疾病和器官移植的靶点。

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.