CaM-regulated chromatin remodeling: mechanisms, generality and in vivo functions

描述（由申请人提供）：哺乳动物染色质-重塑BAF复合体控制着多种生物过程，通常对环境信号作出反应。众所周知，这些信号调节BAF向靶基因的募集。例如，在巨噬细胞中的TLR 4信号传导后，BAF复合物被募集到许多TLR 4靶基因，在那里它重塑它们的染色质以促进基因表达。出乎意料的是，我们发现BAF募集不足以重塑TLR 4靶基因的一个子集;另外还需要由钙/钙调蛋白（CaM）传递的第二个信号。CaM直接结合BAF复合物以刺激重塑而不影响BAF募集。这是第一次显示钙调素调节染色质重塑，和第一次已知的信号通路调节重塑独立的招聘。在这项资助中，我们将讨论钙调素如何刺激重塑（目标1），这是目前的一个谜。我们的假设是，一些重塑的阻遏物被拴在钙调素依赖的BAF靶基因上，钙调素利用BAF复合物搭便车到靶基因上，在那里它使阻遏物失活，使染色质重塑。我们将使用分子遗传学方法在巨噬细胞中测试这些想法。这项拨款还将测试的想法，钙调素-BAF信号通路中发现的巨噬细胞是普遍的重要性，鉴于钙调素和BAF广泛表达（目标2）。我们的初步数据表明，钙调素-BAF通路确实在T细胞中运作，我们将进一步探索使用小鼠轴承点突变，阻止钙调素-BAF相互作用。我们的研究将阐明新的钙-钙调素-BAF通路的机制，通用性和生物学意义，并感兴趣的信号和染色质领域。

DESCRIPTION (provided by applicant): The mammalian chromatin---remodeling BAF complex controls diverse biological processes, often in response to environmental signals. Such signals are well known to regulate BAF recruitment to target genes. For example, upon TLR4 signaling in macrophages, the BAF complex is recruited to many TLR4 target genes, where it remodels their chromatin to promote gene expression. Unexpectedly, we have found that BAF recruitment is insufficient for remodeling a subset of TLR4 target genes; a second signal, delivered by calcium/calmodulin (CaM), is additionally required. CaM directly binds the BAF complex to stimulate remodeling without affecting BAF recruitment. This is the first time CaM is shown to regulate a chromatin remodeler, and the first time a signaling pathway is known to regulate a remodeler independently of recruitment. In this grant, we will address how CaM stimulates remodeling (Aim 1), which is currently a total mystery. Our hypothesis is that some repressors of remodeling are tethered to CaM---dependent BAF target genes, and CaM uses the BAF complex to hitchhike to the target genes, where it inactivates the repressor to allow chromatin remodeling. We will test these ideas in macrophages, using molecular genetic methods. This grant will also test the idea that the CaM---BAF signaling pathway found in macrophages is of general importance, given that both CaM and BAF are widely expressed (Aim 2). Our preliminary data suggest the CaM---BAF pathway indeed operates in T cells, which we will further explore using mice bearing point mutations that block CaM---BAF interaction. Our study will shed light on the mechanisms, generality and biological importance of the novel Calcium---CaM---BAF pathway, and of interest to both signaling and chromatin fields.