The Role of Histone Chaperones in Histone Acetylation and Nucleosome Dynamics

描述（由申请人提供）：每个真核细胞的细胞核内都有一个基本的悖论：遗传物质必须被组织和压缩，但仍然可以通过转录机制读出。保持这种平衡的许多因素中的两个是组蛋白和组蛋白结合蛋白。组蛋白最终负责将染色体DNA压缩近50万倍以适应细胞核。虽然基因组可及性部分由组蛋白乙酰转移酶（KAT）的作用调节，但组蛋白伴侣蛋白直接与组蛋白相互作用，并且可以在DNA上组装和/或分解组蛋白。KAT共价修饰组蛋白，因此具有改变染色质结构的潜力。令人兴奋的新证据在结构和功能上将KAT和组蛋白伴侣联系起来。然而，几乎没有什么是已知的机制，这些蛋白质的合作，以管理压缩和基因组的可及性。为了开始理解这一重要的生物学问题，本项目提出以组蛋白乙酰转移酶（KAT）Rtt 109为模型系统进行研究。Rtt 109使用两个结构上不相关的组蛋白伴侣，Vps 75和Asf 1。在体内，Vps 75已被证明与Rtt 109直接相互作用，但Rtt 109功能仅需要Asf 1。这两种分子伴侣在体外激活Rtt 109乙酰转移酶活性，但Rtt 109乙酰化组蛋白在多个位置，和Vps 75和Asf 1似乎改变Rtt 109特异性。如何实现特异性和选择性的生物化学和分子理解是目前染色质领域的主要挑战。该项目将采用和扩展新的方法来研究调节染色质动力学和翻译后特异性所需的复杂蛋白质-蛋白质网络。

DESCRIPTION (provided by applicant): There is a fundamental paradox within the nucleus of every eukaryotic cell: The genetic material must be organized and compacted yet remain accessible for readout by transcription machinery. Two of the many factors that retain this balance are histones and histone binding proteins. Histones are ultimately responsible for compacting the chromosomal DNA almost 500,000-fold to fit into the nucleus. While genome accessibility is regulated in part by the actions of histone acetyltransferases (KATs), histone chaperones interact directly with histones and can assemble and/or disassemble them on DNA. KATs covalently modify the histones and therefore have the potential to alter chromatin structure. Exciting new evidence structurally and functionally link KATs and histone chaperones. However, virtually nothing is known about the mechanisms by which these proteins cooperate to manage compaction and genome accessibility. To begin to understand this important biological question, this project proposes to study the histone acetyltransferase (KAT) Rtt109 as a model system. Rtt109 employs two structurally unrelated histone chaperones, Vps75 and Asf1. In vivo, Vps75 has been shown to directly interact with Rtt109, but only Asf1 is required for Rtt109 function. Both chaperones activate Rtt109 acetyltransferase activity in vitro, but Rtt109 acetylates histones in multiple locations, and Vps75 and Asf1 appear to alter Rtt109 specificity. A biochemical and molecular understanding of how specificity and selectivity is achieved is currently a major challenge in the chromatin field. This project will employ and expand on new methodologies for studying complex protein-protein networks needed to regulate chromatin dynamics and post-translational specificity.