Dissecting the roles of histone H3 lysine 27 mono-methylation in DNA replication

基因组DNA通过与组蛋白蛋白的结合而紧凑。组蛋白的共价修饰会影响DNA的紧凑，从而影响需要接触DNA的其他蛋白质的可及性。一个例子是参与基因组DNA复制的蛋白质。这个项目的总体影响是了解某些共价修饰如何有助于调节DNA复制。此外，描绘组蛋白修饰的模式将为其他研究DNA组织基本机制的研究人员提供资源。该项目产生的数据将通过四膜虫基因组数据库(TGd：http://ciliate.org/))和四膜虫基因表达数据库(TGd：http://tged.ihb.ac.cn/).)积极分发给更广泛的研究社区这将是推动单细胞真核生物四膜虫成为科学研究的模式生物以及本科生的教学工具的努力的一部分。本科生也将主要通过与密歇根大学的本科生研究机会计划(UROP)合作，为研究计划做出贡献。还将在纤毛虫基因组联合会(纤毛虫基因组联合会：http://tet.jsd.claremont.edu)，)的框架内开展合作，这是一项由国家科学基金会资助的合作研究倡议，涉及来自不同机构的本科生。这个项目将让本科生参与生物学研究的许多方面，这个水平通常是为研究生保留的，为他们提供经验，帮助他们成功地追求专业和研究生培训。这个项目的核心是组蛋白H3赖氨酸27甲基化，这是一种在原生动物、后生动物和植物中保守的修饰。长期以来，这种修饰与转录抑制和异染色质的形成有关。出乎意料的是，最近发现了组蛋白H3赖氨酸27单甲基化(H3K27me1)在DNA复制中的作用。在四膜虫中，负责甲基化事件的酶TXR1的缺失会导致DNA复制压力和H3K27me1缺陷。对TXR1细胞的表型分析提供了一个切入点，以剖析组蛋白修饰和DNA复制之间的分子联系。通过确定在时间和空间上与DNA合成相关的组蛋白修饰，该项目将阐明支持DNA复制的染色质环境。TXR1的突变将剖析其功能，揭示其靶向活跃复制位点的机制，而H3K27的直接突变将有助于阐明H3K27me1与DNA复制之间的联系。该项目的成功完成将确保对组蛋白修饰控制DNA复制调控的分子机制有深入的了解。

Genomic DNA is compacted by association with histone proteins. Covalent modifications of histones affect DNA compaction and therefore accessibility to other proteins that need to contact the DNA. One example is proteins involved in replication of the genomic DNA. The overall impact of this project is to understand how certain covalent modifications contribute to the regulation of DNA replication. In addition, delineating patterns of histone modifications will be a resource for other investigators that study basic mechanisms of DNA organization. Data generated by this project will be actively distributed to the wider research community through the Tetrahymena Genome Database (TGD: http://ciliate.org/) and the Tetrahymena Gene Expression Database (TGED: http://tged.ihb.ac.cn/). This will be part of an effort to promote the unicellular eukaryote Tetrahymena as a model organism for scientific research, as well as a teaching tool for undergraduate students. Undergraduate students will also contribute to the research program, mainly through collaboration with the Undergraduate Research Opportunity Program (UROP) at the University of Michigan. A collaboration within the framework of the Ciliate Genome Consortium (CGC: http://tet.jsd.claremont.edu), an NSF-funded collaborative research initiative involving undergraduate students from diverse institutes, will also be pursued. This project will involve undergraduate students in many aspects of biology research at a level often reserved for graduate students, providing them experiences that will help them succeed in the pursuit of professional and graduate school training.The histone modification that is at the center of this project is histone H3 lysine 27 methylation, a modification that is conserved in protozoa, metazoa and plants. This modification has long been associated with transcriptional repression and heterochromatin formation. Unexpectedly, a role in DNA replication has been recently revealed for histone H3 lysine 27 mono-methylation (H3K27me1). Deleting TXR1, the enzyme responsible for this methylation event in Tetrahymena, leads to DNA replication stress as well as H3K27me1 deficiency. Phenotypic analysis of ΔTXR1 cells provides an entry point to dissect the molecular connection between histone modifications and DNA replication. By identifying histone modifications that correlate with DNA synthesis both temporally and spatially, this project will shed light on the chromatin environment that supports DNA replication. TXR1 mutagenesis will dissect its function, revealing mechanisms for its targeting to active replication sites, while direct mutation of H3 K27 will help to elucidate the connection between H3K27me1 and DNA replication. Successful completion of this project will secure insights into the molecular mechanisms by which histone modifications control regulation of DNA replication.