Mechanisms of chromatin remodeling at RNA polymerase II promoters

7.项目总结/摘要 所有生物学过程的一个基本方面是基因表达，其在多种生物学过程中受到控制。 第一步是转录。转录不仅受到序列特异性因子的调控， 作为激活子和抑制子，但也通过染色体DNA的潜在染色质结构。这 结构由各种染色质重塑途径决定。编码染色质调节因子的基因 重塑途径在人类癌症中经常发生突变。染色质调节因子的扰动促进 癌症进展部分是通过恢复组织发育过程中所承诺的“开”或“关”染色质状态 从而增加基因表达的可塑性，使癌细胞能够进化 并适应。组蛋白H2A.Z是一种重要的染色质调节因子，其使基因转录平衡。其插入 进入大多数基因启动子下游的核小体。H2A.Z超积累 使癌细胞更具侵袭性，并与癌症患者的预后不良有关。 使用芽殖酵母模型系统，我以前证明了高度保守的ATP- 依赖性重塑体SWR在体外以单向方式用H2A.Z取代核小体H2 A。期间 在当前的资金周期内，我的实验室发现H2A.Z在积极和积极的方面都面临着快速的流动， 很少转录的基因并且转录机制靶向H2A.Z核小体 体内解体此外，我们开发了一种新的方法，用于全球确定H2A.Z和 酵母和人类细胞中含有H2 A的核小体，称为VivosX。本建议将这项工作扩展到（1） 剖析了SWR染色质重塑酶将H2A.Z插入 染色质上的特异性位点和（2）阐明H2A.Z插入后启动子处的分子事件。这 这些知识可能最终揭示出能够抵消H2A.Z异常水平的药物的分子靶点。 在癌细胞中。

7. PROJECT SUMMARY/ABSTRACT A fundamental aspect of all biological processes is gene expression, which is controlled at a variety of levels, the first step being transcription. Transcription is regulated not only by sequence-specific factors such as activators and repressors, but also by the underlying chromatin structure of the chromosomal DNA. This structure is determined by various chromatin remodeling pathways. Genes encoding regulators of chromatin remodeling pathways are frequently mutated in human cancers. Perturbation of chromatin regulators promotes cancer progression in part by reverting the `on' or `off' chromatin states committed during tissue development to a poised, stem-like state, thereby increasing gene expression plasticity that enables cancer cells to evolve and adapt. Histone H2A.Z is an important chromatin regulator that poises genes for transcription. It is inserted into nucleosomes immediately downstream of the promoters of most genes. Hyper-accumulation of H2A.Z makes cancer cells more invasive and is linked with poor prognosis in cancer patients. Using the budding yeast model system, I previously demonstrated that the highly conserved, ATP- dependent remodeler SWR replaces nucleosomal H2A with H2A.Z in a unidirectional manner in vitro. During the current funding period, my lab found that H2A.Z is subjected to rapid turnover at both actively and infrequently transcribed genes and that the transcription machinery targets H2A.Z nucleosomes for disassembly in vivo. In addition, we developed a novel method for globally determining the levels of H2A.Z and H2A-containing nucleosomes in yeast and human cells called VivosX. This proposal will extend this work to (1) dissect the molecular mechanisms by which the SWR chromatin remodeling enzyme inserts H2A.Z into specific sites on chromatin and (2) elucidate the molecular events at promoters after H2A.Z insertion. This knowledge may ultimately reveal molecular targets for drugs that can counteract the aberrant levels of H2A.Z in cancer cells.