BAF complexes in T cell development

描述（由申请人提供）：哺乳动物Swi/Snf相关BAF复合物是普遍表达的原型“ATP依赖性染色质重塑复合物”，其可响应外部信号使用能量来操纵核小体结构。BAF突变与多种人类肿瘤有关，但对BAF复合物的生理功能知之甚少。我们的长期目标是使用T细胞发育作为模型系统，以确定BAF复合物的生理靶基因，剖析BAF复合物调节这些基因的机制，并了解BAF复合物如何响应信号通路。我们已经发现，删除ATP酶亚基Brg在T细胞发育中产生多种缺陷，其中一些缺陷被HMG盒蛋白BAF 57的突变所重现。特别是，BAF 57以及BAF复合物的许多其他亚基在体外参与经典的Brg催化的ATP依赖性重塑。我们假设，“BRG”亚基可以调节基因表达的新机制，独立于Brg介导的染色质重塑，并通过刺激重塑的目标基因在其天然染色质的情况下。使用遗传学和生物化学方法相结合，我们将试图确定在T细胞发育过程中的基因调控中假定的ATP-独立的BAF功能，以探测这种功能的分子基础，并最终确定BAF 57是否可以帮助Brg重塑内源性靶基因。这些研究将增强我们对T细胞发育的理解，并且具有普遍意义：它们在染色质领域面临着一个重大挑战，即解决染色质重塑体的体内功能，特别是由其α亚基介导的功能。此外，鉴于BAF复合物在肿瘤发生中的作用，我们的研究具有实用价值。

DESCRIPTION (provided by applicant): Mammalian Swi/Snf-related BAF complexes are ubiquitously expressed, prototypical "ATP-dependent chromatin remodeling complexes" that can use energy to manipulate nucleosome structure in response to external signals. BAF mutations are linked to multiple human tumors, but the physiological functions of BAF complexes are poorly understood. Our long-term goals are to use T cell development as model systems to identify physiological target genes of BAF complexes, to dissect the mechanisms by which BAF complexes regulate these genes, and to understand how BAF complexes respond to signaling pathways. We have found that deleting the ATPase subunit Brg produces multiple defects in T cell development, some of which are recapitulated by mutations in BAF57, an HMG-box protein. Paradoxically, BAF57 as well as many other subunits of BAF complexes are dispensable for the classical Brg-catalyzed, ATP-dependent remodeling in vitro. We hypothesize that the "dispensable" subunits can regulate gene expression by novel mechanisms independent of Brg-mediated chromatin remodeling, and by stimulating remodeling of the target genes in their natural chromatin contexts. Using a combination of genetic and biochemical methods, we will attempt to identify the putative ATP-independent BAF functions in gene regulation during T cell development, to probe the molecular basis of such functions, and finally to determine whether BAF57 can help Brg to remodel endogenous target genes. These studies will enhance our understanding of T cell development, and are of general interest: they take on a major challenge in the chromatin field, which is to address the in vivo functions of chromatin remodelers especially those mediated by their dispensable subunits. In addition, our studies are of practical value, given the roles of BAF complexes in tumorigenesis.