Histone Tail Interactions and Functions in Chromatin

摘要： 真核细胞核内的DNA与组蛋白和其他蛋白质组装以 形成一种复杂的、多方面的复合体，称为染色质。染色质不仅 用于包装基因组，但染色质结构的元素已经紧密地 整合到基因控制机制中。核心组蛋白尾部结构域对于 染色质内多层结构的形成和大部分信号 核内的转导最终指导这些基因的翻译后修饰 结构域，以促进核过程，如转录。在几个案例中， 进行这些修饰的酶的突变与各种 包括人类癌症在内的疾病。然而，其分子机制 尾部结构域定义了染色质结构，并最终定义了 潜在的DNA-仍然知之甚少。中描述的工作的主要目标 这一建议是为了阐明核心组蛋白尾巴的分子机制 结构域决定了高阶染色质结构的形成以及乙酰化的方式 这些结构域中的特定赖氨酸改变了尾部结构和相互作用，以允许 基因表达。我们的目标是1)刻画短程和远程之间的距离 模型核小体中H3和H4尾区的核小体相互作用 核小体阵列，2)确定连接物组蛋白H1、结构 转录因子HMGN或染色质重塑活性特异性改变 尾部结构域的相互作用和TO 3)定量评估所选尾部的结合 重组和天然结构域以及乙酰化对这些相互作用的影响 染色质。我们将使用几种新的方法，包括现场定向化学 绘制Tail-DNA相互作用图、UV激光交联法和其他化学物质 探索研究尾区结构和相互作用的方法。 此外，我们将使用化学保护方法和特殊标记的核心的核磁共振 用组蛋白定量评价单个组蛋白的盐依赖结合稳定性 核小体内的尾巴。这项工作将促进我们对关键分子的理解 影响基因表达控制以及最终影响疾病等的机制 就像癌症一样。

Abstract: DNA within the eukaryotic cell nucleus is assembled with histones and other proteins to form a complicated, multifaceted complex known as chromatin. Chromatin not only serves to package the genome but elements of chromatin structure have been intimately integrated into gene control mechanisms. The core histone tail domains are essential for the formation of multiple levels of structure within chromatin and a large portion of signal transduction within the nucleus ultimately directs posttranslational modification of these domains in order to facilitate nuclear processes such as transcription. In several cases, mutations in enzymes that carry out these modifications have been linked to various diseases including cancers in humans. However, the molecular mechanisms by which the tail domains define chromatin structures - and ultimately the functionality of the underlying DNA - remain poorly understood. The primary goal of the work described in this proposal is to elucidate the molecular mechanisms by which the core histone tail domains dictate the formation of higher order chromatin structures and how acetylation of specific lysines within these domains alters tail structures and interactions to allow for gene expression. Our aims are to 1) characterize short-range and long-range inter- nucleosomal interactions of the H3 and H4 tail domains in model nucleosomes and nucleosome arrays, 2) Determine whether linker histone H1, the architectural transcription factor HMGN or a chromatin remodeling activity specifically alters interactions of the tail domains and to 3) quantitatively assess binding of selected tail domains and the effect of acetylation on these interactions in reconstituted and native chromatin. We will use several novel approaches including site-directed chemical mapping of tail-DNA interactions, a UV laser crosslinking approach, and other chemical probing approaches to investigate structures and interactions of the tail domains. Further, we will use a chemical protection approach and NMR of specifically labeled core histones to quantitatively assess the salt-dependent binding stability of individual histone tails within nucleosomes. This work will advance our understanding of critical molecular mechanisms that impinge upon control of gene expression and ultimately diseases such as cancer.