DNA double-strand break chromatin alterations and genome integrity

联系PD/PI：Greenberg，Roger A. 总结 进化保守的DNA修复机制在整个细胞周期中合作， 基因组完整性然而，对于受损的染色质如何指导一系列的细胞凋亡， 决定随后修复机制的事件。这种知识上的差距特别关系到一个贫穷的国家。 理解的同源性指导的修复机制变得活跃，以维持端粒长度， 大约15%的人类癌症。端粒的替代性延长（ALT）发生在非典型的 间充质来源癌症中同源性指导的DNA修复机制。重组机制 在ALT依赖性癌症中，负责端粒维持的基因是独特的脆弱性。 我们已经开发出实验系统，能够定量，实时可视化的每一个步骤， 同源定向修复受损的端粒。我们发表的研究表明，ALT是由DNA启动的， 损伤依赖性同源指导的修复合成，其单向进行到损伤的末端。 染色体我们将这一机制命名为断裂诱导端粒合成，并表明它对 利用ALT的细胞中端粒延长。在这里，我们研究了DNA损伤如何反应的问题， 在端粒染色质上组装以指导长束同源定向修复端粒合成。 我们假设断裂诱导的端粒合成是通过组装几种不同的 DNA修复机制是在端粒染色质上实现同源性定向修复合成。我们未发表 结果明确支持了这一假设，显示了广泛的PCNA-泛素化和5 '-3'端的募集。 核酸酶SNM 1A和5 '-3'解旋酶FANCJ在受损的端粒处促进DNA修复合成， 端粒完整性我们将研究它们与端粒的损伤依赖性联系的基础， 在端粒的重组依赖性修复合成中发挥作用，使用多方面的方法， 我们在细胞和体外高度纯化的系统中检查端粒损伤反应的每一步， 在确定的底物上组装断裂诱导的复制体。这些基础研究旨在 了解断裂诱导端粒合成的关键要素，以及它如何使端粒延长 在依赖ALT的细胞中持续增殖

Contact PD/PI: Greenberg, Roger A. Summary Evolutionary conserved DNA repair mechanisms cooperate throughout the cell cycle to faithfully maintain genome integrity. However, a minimal understanding exists for how damaged chromatin directs the series of events that dictate ensuing repair mechanism. This gap in knowledge is particularly relevant to a poorly understood homology directed repair mechanism that becomes active to maintain telomere length in approximately 15% of human cancers. Alternative lengthening of telomeres (ALT) occurs by noncanonical homology directed DNA repair mechanism in cancers of mesenchymal origin. The recombination mechanisms responsible for telomere maintenance represent a unique vulnerability in ALT reliant cancers. We have developed experimental systems that enable quantitative, real-time visualization of each step in the homology directed repair of damaged telomeres. Our published studies reveal that ALT is initiated by DNA damage dependent homology directed repair synthesis that proceeds unidirectionally to the end of the chromosome. We named this mechanism Break Induced Telomere Synthesis and showed that it is critical for telomere lengthening in cells that utilize ALT. Here, we examine the question of how DNA damage responses assemble on telomeric chromatin to direct long-tract homology directed repair telomere synthesis. We hypothesize that Break Induced Telomere Synthesis occurs by assembling elements of several different DNA repair mechanisms on telomeric chromatin to achieve homology directed repair synthesis. Our unpublished results definitively support this premise, showing extensive PCNA- ubiquitination and recruitment of the 5’-3’ nuclease SNM1A and 5’-3’ helicase FANCJ at damaged telomeres to promote DNA repair synthesis and telomere integrity. We will investigate the basis for their damage dependent association with telomeres and functions in recombination dependent repair synthesis at telomeres using a multifaceted approach that allows us to examine each step of the telomere damage response in cells and in vitro in highly purified systems that assemble the break induced replisome on defined substrates. These fundamental studies are designed to understand the critical elements of Break Induced Telomere Synthesis and how it allows telomere lengthening for sustained proliferation in cells that rely on ALT.