Role of Chromatin and Gene Poising in T Cell Differentiation and Activation

描述(申请人提供)：摘要：候选人现为国立卫生研究院博士后研究员，赵克基博士实验室博士后。该提案描述了一个导致独立的研究和培训相结合的计划。在该项目的指导阶段，候选人将继续接受应用CHIP-SEQ和RNA-SEQ等现代高通量技术所必需的计算数据分析方面的培训，并发展成功的学术生涯所需的其他技能。本项目的研究目标是了解染色质和基因平衡在辅助性T细胞分化和功能中的作用。在初始抗原刺激下，幼稚T细胞分化为效应器，然后分化为记忆性T细胞。由于先前的抗原暴露，记忆T细胞能够比初始T细胞更快地产生细胞因子和对抗感染。这种记忆T细胞的能力可能是由表观遗传机制介导的。最近，我们开发了CHIP-SEQ，这是一种研究染色质修饰在全基因组范围内分布的新方法。将这种方法应用于静止的T细胞，我们发现一些沉默的基因具有“活跃的”染色质修饰，通常与表达的基因相关，甚至在它们的启动子上有RNA聚合酶II(POL II)。我们称这些基因为稳定基因，因为在T细胞激活过程中实际诱导的大多数基因都属于这个基因组。为了测试平衡是否可能从头开始发生，还是必须是先前表达的结果，我们建议跟踪幼稚T辅助细胞体外分化为Th1/Th2细胞过程中染色质和POL II结合和基因表达的变化。此外，我们假设效应器记忆T辅助细胞快速产生细胞因子的能力是通过这些基因的平衡来调节的。我们将把细胞因子和记忆T细胞亚群中其他重要基因的染色质结构与这些基因在这些细胞类型中快速表达的能力联系起来(目标1)。平衡基因在其启动子上具有POLII和所有必要的染色质修饰，但不转录。当T细胞被激活时，只有一小部分稳定的基因被表达。我们将剖析平衡基因转录抑制的机制，并确定在T细胞激活时以基因特异性方式释放这种抑制的因素(目标2)。综上所述，这些研究的结果将有助于我们理解获得性免疫反应。 公共卫生相关性： 叙述：这个项目旨在探索染色质修饰和基因平衡在T辅助细胞分化和激活中的作用。这些研究将有助于更好地理解获得性免疫反应和获得性免疫。

DESCRIPTION (provided by applicant): Summary The candidate is currently a postdoctoral fellow at NHLBI in the laboratory of Dr. Keji Zhao. The proposal describes a combined research and training program leading to independence. During the mentored phase of this project, the candidate will continue training in computational data analysis necessary for the application of modern high- throughput techniques such as ChIP-Seq and RNA-Seq, as well as develop other skills necessary for a successful academic career. The research goal of this project is to understand the role of chromatin and gene poising in T helper cell differentiation and function. Upon initial antigen stimulation, naive T cells differentiate into effector and then into memory T cells. As a result of previous antigen exposure, memory T cells are able to produce cytokines and fight infection more rapidly than naive T cells. This ability of memory T cells is likely mediated by the epigenetic mechanisms. Recently, we developed ChIP-Seq, a novel method to study genome-wide distribution of chromatin modifications. Applying this method to resting T cells, we discovered that some silent genes posses "active" chromatin modifications normally associated with expressed genes and even have RNA Polymerase II (Pol II) at their promoters. We called these genes poised, because the majority of the genes that were actually induced during T cell activation belonged to this gene set. To test whether poising may occur de novo or has to be a result of prior expression we propose to follow changes in chromatin and Pol II binding and gene expression during in vitro differentiation of naive T helper cells into Th1/Th2 cells. Further, we hypothesize that the ability of effector memory T helper cells to quickly produce cytokines is mediated by poising of these genes. We will correlate chromatin structure at cytokine and other important genes in naive and subsets of memory T cells with the ability of these genes to be rapidly expressed in these cell types (Aim 1). Poised genes possess Pol II and all the necessary chromatin modifications at their promoters, but are not transcribed. Upon T cell activation only a minority of poised genes are expressed. We will dissect the mechanism of transcription inhibition at the poised genes and identify factors responsible for the release of this inhibition in a gene specific manner upon T cell activation (Aim 2). Taken together, results of these studies will contribute to our understanding of acquired immune response. PUBLIC HEALTH RELEVANCE: Narrative: This project aims to explore the role of chromatin modifications and gene poising in T helper cell differentiation and activation. The studies will lead to better understanding of adaptive immune response and acquired immunity.