HISTONE TAIL INTERACTIONS AND FUNCTIONS IN CHROMATIN

描述（改编自申请人的摘要）：染色质的元素是 现在已知它直接参与基因表达的控制。确实 细胞核内的大部分信号转导似乎 最终指导核心组蛋白的翻译后修饰 蛋白质，在某些情况下，进行这些酶的突变 基因修饰与人类的各种癌症有关。 在过去的2-3 多年来，人们一直致力于阐明和生物化学 调节核心组蛋白的调节机制和酶的纯化 修饰，尤其是乙酰化。 有趣的是，几乎所有这些 翻译后修饰发生在被称为“翻译后修饰区”的特定区域内。 核心组蛋白“尾”域。 生物物理实验表明， 结构域是核小体串组装成核小体的关键组分。 高度紧密且功能惰性的染色质纤维。 比如说， 尾部的乙酰化极大地使纤维不稳定， DNA更容易接近反式作用因子和酶， 转录、复制或DNA修复。 这项提案的主要目标是阐明的分子细节， 核心组蛋白尾部结构域决定结构的机制 染色质纤维的功能状态。 最近的证据表明， 尾巴使核小体内和核小体间的相互作用精确而局部化 在染色质中。 将使用一种新的定点化学作图方法 绘制各种模型染色质复合物中组蛋白尾部相互作用的图谱。 尾相互作用将被映射在扩展和浓缩的核小体阵列 以确定这些相互作用，特别是参与稳定 浓缩染色质纤维 一种化学保护方法和核磁共振 特别标记的核心组蛋白将用于研究盐依赖性 核小体内单个组蛋白尾部的结合稳定性。 在 此外，这些相同的方法将被用来检查特定的影响， 与转录激活和DNA相关的组蛋白乙酰化模式 复制的 这些结果将有助于阐明尾功能的机制 在染色质中。

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.