RUI: Control of CIITA Function and Immune System Gene Expression by Phosphorylation

当身体受到外来病原体的威胁时，各种免疫系统基因的表达使细胞能够对这种威胁做出反应，并启动免疫反应。诱导这种免疫反应的核心是激活主要调节因子--II类反式激活因子(CIITA)。CIITA作用于细胞的细胞核，诱导外源多肽在细胞表面的表达。已知CIITA蛋白同时存在于细胞的细胞质和细胞核中，尽管这种双峰分布的意义和调节它的因素尚不清楚。已有的研究表明，在细胞蛋白质中添加或减少磷酸基团可以改变该特定蛋白质的活性和定位。初步数据表明，CIITA确实经历了磷酸化；然而，这种磷酸化对调节CIITA蛋白功能的作用尚不清楚。一种假说是，胞核中特异存在的CIITA的磷酸化关闭了CIITA调控的基因表达，并随后诱导CIITA从胞核输出到细胞质。这可能允许有机体快速而精确地控制CIITA活动的时间和程度，从而调节免疫反应的大小。本项目将通过以下几个方面来检验这一假设：1)确定介导CIITA磷酸化的细胞机制和因素；2)确定磷酸化对CIITA活性的影响；以及3)确定介导CIITA从细胞核输出的蛋白质结构域。了解控制CIITA活性的细胞和分子机制对于设计控制免疫系统和改变免疫反应的策略至关重要。这个项目将确定免疫系统被调节和发出信号以响应外来病原体存在的细胞机制。实验室实验将确定中央控制蛋白CIITA是如何被结构修饰和调控的，以及这些修饰对细胞内蛋白质的功能有什么影响。这项研究将为制定治疗策略，在分子和细胞水平上修改和增强免疫系统的治疗能力提供基础。此外，在该项目的三年时间框架内，本科生将以暑期或学年实习生的身份参加该项目，为进一步开发课程和加强萨拉·劳伦斯学院的本科生科学培训奠定基础。

When a body is threatened by foreign pathogens, expression of a variety of immune system genes allows cells to react to this threat and initiate an immune response. Central to inducing this immune response is the activation of the master regulator factor, the class II transactivator (CIITA). CIITA acts in the nucleus of cells to induce the expression of genes necessary for the presentation of foreign peptides on the cell surface. The CIITA protein is know to be present in both the cytoplasmic and nuclear compartments of cells, although the significance for this bimodal distribution and the factors that regulate it are unclear. It has been well established that the addition or subtraction of phosphate group moieties to a cellular protein can modify the activity and localization of that particular protein. Preliminary data indicates that CIITA is indeed subject to phosphorylation; however, the effect this phosphorylation has on regulating the function of the CIITA protein is unknown. One hypothesis is that phosphorylation of CIITA specifically present in the nucleus shuts down CIITA-regulated gene expression and subsequently induces the export of CIITA from the nucleus out to the cytoplasm. This may allow the organism to rapidly and precisely control the timing and extent of CIITA activity, and therefore mediate the magnitude of the immune response. This project will examine this hypothesis by: 1) identifying the cellular mechanisms and factors that mediate phosphorylation of CIITA; 2) determining the effect phosphorylation has on CIITA activity; and 3) identifying the protein domains that mediate the export of CIITA from the nucleus. Understanding the cellular and molecular mechanisms that control CIITA activity will be crucial to devising strategies to manipulate the immune system and alter immune responses.This project will identify the cellular mechanisms by which the immune system is regulated and signaled to respond to the presence of foreign pathogens. Laboratory experiments will determine how the central control protein, CIITA, is structurally modified and regulated and what effect these modifications have on the function of the protein within cells. This research will provide a basis for generating therapeutic strategies to modify and enhance the therapeutic abilities of the immune system at the molecular and cellular level. Additionally, during the three-year timeframe of this project, undergraduate students will participate in the program as summer or academic year interns, establishing the foundation for further curricular development and strengthening undergraduate scientific training at Sarah Lawrence College.