Functions of Mammalian Histone Modifiers

 描述（由申请人提供）：组蛋白翻译后修饰对于建立促进或抑制基因表达的染色质环境至关重要。这种组织在发育过程中尤其重要，因为未能激活或抑制谱系特异性表达程序会导致胚胎缺陷，通常会导致死亡（11，12）。组蛋白乙酰化是染色质可及性的关键调节因子，但我们仍然有很多关于特定HAT或HDACS在发育或疾病过程中的作用的研究。我们的实验室已经在小鼠和ES细胞中使用遗传方法来定义Gcn 5的功能，Gcn 5是第一个被识别的转录相关HAT（1）。我们以前的研究表明，Gcn 5是正常小鼠发育所必需的（5，6）。我们还发现，Gcn 5的缺失导致含Gcn 5的佐贺复合物中去泛素化酶（DUB）模块的丢失，并且该模块在端粒维持中具有意想不到的作用（7）。在小鼠胚胎干（ES）细胞中的另外的研究揭示，Gcn 5是Myc和E2F1在ES细胞中的自我更新网络的调节和体细胞重编程为干细胞状态中的重要共激活剂（Hirsch等人，提交）。我们推测，Gcn 5也调节关键基因表达程序在发展过程中，反映了Gcn 5突变胚胎的表型的严重性。在本提案的目标1中，我们提出了基因组和单细胞水平的实验来定义在体外ES细胞分化期间需要Gcn 5的发育程序。在目标2中，我们提出了基因组编辑方法来定义Gcn 5中高度保守的溴结构域的功能，这可能有助于促进Gcn 5与组蛋白和其他对正常发育重要的蛋白质中乙酰化赖氨酸的相互作用。大规模的癌症基因组分析表明，Gcn5在许多癌症中过表达（癌症基因组图谱）。特定的佐贺组分也与SCA7相关，SCA7是一种使人衰弱的神经退行性疾病（9，10）。从长远来看，我们对Gcn 5在发育过程中的功能的定义将为Gcn 5和佐贺如何促进肿瘤发生和神经退行性变以及这些疾病的新治疗选择提供新的见解。

 DESCRIPTION (provided by applicant): Histone post-translational modifications are critical for establishing chromatin environments that facilitate or inhibit gene expression. Such organization is especially important during developmental processes, as failure to activate or repress lineage specific expression programs leads to embryonic defects and often death (11, 12). Histone acetylation is a key regulator of chromatin accessibility, but we still have much to learn about the roles of specific HATs or HDACS in developmental or disease processes. Our lab has used genetic approaches in mice and in ES cells to define the functions of Gcn5, the first transcription-related HAT to be identified (1). Our previous studies demonstrated that Gcn5 is essential for normal mouse development (5, 6). We also discovered that deletion of Gcn5 leads to loss of a deubiquitylase (DUB) module from the Gcn5- containing SAGA complex and that this module has an unexpected role in telomere maintenance (7). Additional studies in mouse embryonic stem (ES) cells revealed that Gcn5 is an important co-activator for Myc and E2F1 in the regulation of a self-renewal network in ES cells and in reprogramming of somatic cells to a stem cell state (Hirsch et al, submitted). We hypothesize that Gcn5 also regulates critical gene expression programs during development, as reflected by the severity of the phenotypes of Gcn5 mutant embryos. In Aim 1 of this proposal, we propose both genomic and single cell level experiments to define developmental programs that require Gcn5 during ES cell differentiation in vitro. In Aim 2, we propose genome editing approaches to define the functions of a highly conserved bromodomain in Gcn5, which likely serves to promote Gcn5 interactions with acetylated lysines in histones and other proteins important for normal development. Large-scale cancer genomic analyses indicate that Gcn5 is overexpressed in a number of cancers (The Cancer Genome Atlas). Specific SAGA components are also linked to SCA7, a debilitating neurodegenerative disease (9, 10). In the longer term, our definition of the functions of Gcn5 during development will provide new insights into how Gcn5 and SAGA contribute to oncogenesis and neurodegeneration, as well as new therapeutic options for these conditions.