HISTONE TAIL INTERACTIONS AND FUNCTIONS IN CHROMATIN

描述(改编自申请人的摘要)：染色质的成分是 现在已知直接参与了基因表达的控制。事实上，一个 细胞核内的很大一部分信号转导似乎是 最终指导核心组蛋白的翻译后修饰 蛋白质，在几种情况下，实现这些的酶的突变 基因修饰已经被认为与人类的各种癌症有关。在最后的2-3 多年来，人们在阐明和生化方面投入了大量的努力 核心组蛋白调节机制和酶的纯化 修饰，尤指乙酰化。有趣的是，几乎所有这些 翻译后修改发生在称为 核心组蛋白‘尾部’结构域。生物物理实验表明，尾巴 结构域是将一串串核体组装成 高度致密且功能惰性的染色质纤维。例如, 尾部的乙酰化极大地破坏了纤维的稳定性，从而提供了 DNA更容易接触到携带反式作用因子和酶的 转录、复制或DNA修复。 这项提议的主要目标是阐明细胞的分子细节 核心组蛋白尾部结构域决定结构和 染色质纤维的功能状态。最近的证据表明，这些 尾巴使核小体内和核小体间的相互作用精确和局部化 在染色质内。将使用一种新的现场定向化学测绘方法 绘制各种模型染色质复合体中组蛋白尾部的相互作用图。 尾巴相互作用将被映射到扩展和浓缩的核小体阵列中 以确定那些具体涉及稳定 浓缩的染色质纤维。化学保护方法与核磁共振 特殊标记的核心组蛋白将被用于研究盐依赖 核小体内单个组蛋白尾巴的结合稳定性。在……里面 此外，这些相同的方法将被用来检查特定的 组蛋白乙酰化模式与转录激活和DNA的关系 复制。这些结果将有助于阐明尾巴功能的机制。 染色质。

DESCRIPTION (Adapted from the applicant's abstract): Elements of chromatin are now known to be directly involved in the control of gene expression. Indeed, a large portion of signal transduction within the cell nucleus appears to ultimately direct the posttranslational modification of the core histone proteins and, in several cases, mutations in enzymes that carry out these modifications have been linked to various cancers in humans. In the last 2-3 years much effort has been devoted to the elucidation and biochemical purification of the regulatory machinery and enzymes that mediate core histone modifications, especially acetylation. Interestingly, practically all of these posttranslational modifications occur within specialized regions known as the core histone 'tail' domains. Biophysical experiments have shown that the tail domains are key components in the assembly of strings of nuclesomes into the highly compacted and functionally inert chromatin fiber. For example, acetylation of the tails greatly destabilizes the fiber and thus affords greater accessibility of the DNA to trans-acting factors and enzymes that carry out transcription, replication, or DNA repair. The primary goal of this proposal is to elucidate the molecular details of the mechanisms by which the core histone tail domains dictate the structure and functional state of the chromatin fiber. Recent evidence suggests that these tails make precise and localized intra- and inter-nucleosomal interactions within chromatin. A novel site-directed chemical mapping approach will be used to map histone tail interactions in a variety of model chromatin complexes. Tail interactions will be mapped in extended and condensed nucleosomal arrays to determine those interactions specifically involved in stabilizing the condensed chromatin fiber. A chemical protection approach and NMR of specifically labeled core histones will be used to study the salt-dependent binding stability of individual histone tails within the nucleosome. In addition, these same methods will be used to examine the effects of specific patterns of histone acetylation related to transcriptional activation and DNA replication. These results will help elucidate the mechanisms of tail function in chromatin.