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

基因组DNA通过与组蛋白结合而被压缩。组蛋白的共价修饰影响DNA的压缩，因此影响其他需要接触DNA的蛋白质的可及性。一个例子是参与基因组DNA复制的蛋白质。该项目的总体影响是了解某些共价修饰如何有助于DNA复制的调节。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（TGED：http：//tged.ihb.ac.cn/）积极分发给更广泛的研究界。这将是促进单细胞真核生物四膜虫作为科学研究模式生物以及本科生教学工具的努力的一部分。本科生也将为研究计划做出贡献，主要是通过与密歇根大学的本科生研究机会计划（UROP）合作。纤毛虫基因组联盟（CGC：http://tet.jsd.claremont.edu），一个由NSF资助的合作研究计划，涉及来自不同机构的本科生的框架内的合作，也将继续进行。 这个项目将涉及生物学研究的许多方面的本科生在一个水平往往保留给研究生，提供他们的经验，这将有助于他们在追求专业和研究生院的培训取得成功。组蛋白修饰是在这个项目的中心是组蛋白H3赖氨酸27甲基化，是一种修饰，是保守的原生动物，后生动物和植物。这种修饰长期以来与转录抑制和异染色质形成有关。出乎意料的是，最近发现组蛋白H3赖氨酸27单甲基化（H3 K27 me 1）在DNA复制中的作用。删除四膜虫中负责这种甲基化事件的酶TXR 1会导致DNA复制应激以及H3 K27 me 1缺陷。TXR 1细胞的表型分析提供了一个切入点来剖析组蛋白修饰和DNA复制之间的分子联系。通过鉴定与DNA合成在时间和空间上相关的组蛋白修饰，该项目将揭示支持DNA复制的染色质环境。TXR 1突变将剖析其功能，揭示其靶向活性复制位点的机制，而H3 K27的直接突变将有助于阐明H3 K27 me 1和DNA复制之间的联系。本项目的成功完成将确保深入了解组蛋白修饰控制DNA复制调节的分子机制。

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.