Roles of Chromatin Regulation in Embryonic Stem Cell Self-Renewal

描述（由申请人提供）： 摘要胚胎干细胞（ESCs）具有两个独特的功能，使其成为开发退行性疾病治疗方法的潜在工具。首先，ESC具有分化成任何细胞类型的能力，这种特性称为多能性。第二，胚胎干细胞具有在培养物中以未分化状态无限期增殖的能力，而不积累遗传或细胞毒性。 表观遗传改变，一个叫做自我更新的过程。ESC自我更新或分化的决定最终由称为ESC“主调节因子”的几种转录因子连同染色质结构的调节因子一起沿着控制。近年来，ESC主调节因子的基因靶点和功能已得到更好的理解。相比之下，ESC自我更新或多能性所需的大多数染色质调节剂的靶点和基因调节功能是未知的。该项目旨在了解三种染色质调节复合物的功能和作用机制，这些复合物在ESC自我更新和多能性中具有关键功能。Tip 60- p400复合物具有赖氨酸乙酰转移酶（KAT）和核小体重塑活性，并在自我更新的ESCs中沉默分化诱导的基因。这一发现是出乎意料的，考虑到大多数KAT主要在转录激活中起作用，以及Tip 60-p400复合物在体细胞中基因激活中的记录作用。我们将研究Tip 60-p400复合物沉默小鼠胚胎干细胞分化基因的机制，并确定这种活性在分化过程中是如何调节的。此外，我们最近发现，两个额外的染色质调控复合物，BHD和BAF，相反地调节一组重叠的靶基因，这是在中等水平表达的结果，这种对立。我们将研究这种对立的机制，它在维持多能性状态中的重要性，以及它在ESC分化中的功能。

DESCRIPTION (provided by applicant): Abstract Embryonic stem cells (ESCs) exhibit two unique features that make them potential tools for the development of therapies for degenerative diseases. First, ESCs have the capacity to differentiate into any cell type, a property termed pluripotency. Second, ESCs have the ability to proliferate indefinitely in culture in an undifferentiated state without accumulating genetic or epigenetic alterations, a process called self- renewal. The decision of ESCs to self-renew or differentiate is ultimately controlled by several transcription factors called ESC "master regulators", along with regulators of chromatin structure. In recent years, the gene targets and functions of the ESC master regulators have become better understood. In contrast, the targets and gene regulatory functions of most chromatin regulators required for ESC self-renewal or pluripotency are unknown. This project aims to understand the functions and mechanisms of action of three chromatin regulatory complexes with crucial functions in ESC self-renewal and pluripotency. The Tip60- p400 complex has lysine acetyltransferase (KAT) and nucleosome remodeling activities, and functions to silence differentiation-induced genes in self-renewing ESCs. This finding was unexpected, given the fact that most KATs function primarily in activation of transcription, and the documented roles of Tip60-p400 complex in gene-activation in somatic cells. We will examine the mechanism by which the Tip60-p400 complex silences differentiation genes in murine ESCs, and determine how this activity is regulated during differentiation. In addition, we recently found that two additional chromatin regulatory complexes, NURD and BAF, oppositely regulate an overlapping set of target genes, which are expressed at moderate levels as a result of this opposition. We will examine the mechanisms underlying this opposition, its importance in the maintenance of the pluripotent state, and its function in ESC differentiation.