Chromatin Assembly Structure and Function

描述（由申请人提供）：真核生物基因组与组蛋白一起包装到染色质中对DMA模板上发生的所有过程具有深远的影响，包括复制、转录和修复。染色质的组装和拆卸对基因组的复制至关重要，但人们对其了解甚少。最近的研究（包括我们自己的研究）发现，独立于基因组复制的染色质组装和拆卸是转录调控的一种新颖而重要的手段。该项目的长期目标是对染色质拆卸和重组如何调节转录产生统一的理解。我们发现了一种新的染色质分解前体，在体内，在核小体分解之前，一个转录激活子被结合在核小体的双对称轴附近。因此，我们的第一个目标是确定染色质的变化，这些变化使激活剂能够破坏核小体的稳定性，从而驱动染色质分解。我们的第二个目标是发现启动子染色质拆解和重组分别对转录激活和抑制至关重要的基本分子机制。该研究还将确定组蛋白修饰的最终目标是否为调节染色质的拆卸和重组，并可能确定足以通过复制维持裸DNA状态的表观遗传标记。我们的第三个目标是描述我们发现的蛋白酶体在染色质分解中的新作用。通过继续使用分子遗传学分析，重点关注已明确表征的出芽酵母PH05启动子，结合生物化学和结构方法，我们具有独特的优势，可以填补目前对转录程序基本调控和遗传的理解中的关键空白。真核生物物种转录调控机制的高度保守性表明，我们的发现将直接适用于人类疾病的分析，包括许多涉及染色质利用过程缺陷的癌症。与公共卫生有关。许多疾病都是基因表达错误的结果。从这项工作中对染色质组装和拆卸的机制理解将进一步提高我们修改与人类疾病有关的表观遗传密码的能力，以达到治疗干预的目的。

DESCRIPTION (provided by applicant): The packaging of the eukaryotic genome together with histone proteins into chromatin has profound implications for all processes that occur on the DMA template, including replication, transcription and repair. Chromatin assembly and disassembly are essential for duplication of the genome, yet are poorly understood. Recent studies (including our own) have discovered that chromatin assembly and disassembly, independent of genome duplication, are novel and important means of transcriptional regulation. The long-term goal of this project is to generate a unified understanding of how chromatin disassembly and reassembly regulate transcription. We have uncovered a novel precursor of chromatin disassembly where a transcriptional activator is bound near the dyad axis of symmetry of a nucleosome in vivo, prior to nucleosome disassembly. Our first goal therefore is to identify the chromatin changes that enable activators to destabilize a nucleosome enough to drive chromatin disassembly. Our second goal is to discover the fundamental molecular mechanisms whereby promoter chromatin disassembly and reassembly are essential for transcriptional activation and repression, respectively. The proposed research will also discern whether the ultimate target of histone modifications is to regulate chromatin disassembly and reassembly, and may identify the epigenetic mark that is sufficient to maintain a naked DNA state through replication. Our third goal is to characterize the novel role that we have discovered for the proteasome in chromatin disassembly. By continuing to use molecular genetic analyses focusing on the well-characterized budding yeast PH05 promoter coupled with biochemistry and structural approaches, we are uniquely positioned to fill critical gaps in the current understanding of the fundamental regulation and inheritance of transcription programs. The highly conserved nature of transcriptional regulation mechanisms across eukaryotic species indicates that our findings will be directly applicable to the analysis of human diseases, including many forms of cancer that involve defects in chromatin-utilizing processes. Relevance to the public health. Many diseases are the result of incorrect gene expression. The mechanistic understanding of chromatin assembly and disassembly that will come from this work will further our ability to modify the epigenetic codes involved in human diseases for the purpose of therapeutic intervention.