Role of RTEL1 in Microhomology-Mediated End Joining

项目摘要/摘要 DNA中的双链断裂(DSB)可能是由于暴露在辐射和污染物中而引起的 环境。不准确的双链断裂修复可能导致基因组重排，从而导致智力 残疾、神经退化、免疫缺陷和癌症。DSB通过两条主要途径移除： 非同源末端连接(NHEJ)和同源重组(HR)依赖于不同的 这些因素在力学上是非常不同的。重要的是，DNA断裂也可以进行微同源- 介导末端连接(MMEJ)，末端切除触发暴露的单链DNA尾部有限的同源性 DNA链退火以启动末端连接修复。MMEJ导致DNA序列缺失 在微同源区域之间。因此，MMEJ具有高度的突变性，是癌细胞的标志。 发现MMEJ具有专门的DNA聚合酶POLQ，并且它被频繁使用 即使当NHEJ和HR完好无损时，也支持MMEJ是进化上保守的DSB修复的前提 路径。 NHEJ和HR缺陷的肿瘤细胞在化疗后严重依赖MMEJ生存 DNA破坏剂。因此，MMEJ的失活会使肿瘤细胞对这种治疗敏感。一个主要目标 目前MMEJ研究的重点是确定调节或直接催化MMEJ的新因素，以定义基因 以及它们发挥作用的生化基础，并测试它们作为潜在可用药靶点的价值。我们 已经确定RTEL1是有效的MMEJ所需的一个新的因子。RTEL1编码了一个基本的Deah 能分解各种DNA结构的解旋酶，包括关键的重组中间体--置换 循环(D-LOOP)。我们假设RTEL1通过解离D-loop结构促进MMEJ 与MMEJ竞争。我们的模型解释了几个关于HR抑制作用的神秘观察 MMEJ中的因素，并为理解RTEL1相关的病理提供了一个机制框架 疾病。我们将使用分子遗传学和体外生物化学相结合的方法来测试这一创新想法。 该项目将更好地定义MMEJ的机制及其调节，并可能揭示可以 目标是治疗由环境引起的疾病，如癌症和神经疾病。因此，我们的工作 将对环境健康研究产生重大影响。

PROJECT SUMMARY/ABSTRACT Double-strand breaks (DSBs) can arise in DNA from exposure to radiation and pollutants prevalent in our environment. Inaccurate repair of DSBs can lead to genome rearrangements, which can cause intellectual disability, neurodegeneration, immunodeficiency, and cancer. DSBs are removed by two major pathways: nonhomologous end joining (NHEJ) and homologous recombination (HR), which are dependent on different factors and are mechanistically very distinct. Importantly, DNA breaks can also undergo microhomology- mediated end joining (MMEJ), in which limited homology in the ssDNA tails exposed by end resection triggers DNA strand annealing to initiate end joining repair. MMEJ leads to deletion of the DNA sequence situated between the regions of microhomology. As such, MMEJ is highly mutagenic, and is a hallmark of cancer cells. The discoveries that MMEJ possesses a dedicated DNA polymerase, POLq, and that it is employed frequently even when NHEJ and HR are intact support the premise that MMEJ is an evolutionarily conserved DSB repair pathway. Tumor cells deficient in NHEJ and HR rely heavily on MMEJ for viability upon treatment with chemotherapeutic DNA damaging agents. Inactivation of MMEJ would thus sensitize tumor cells to such treatments. A major goal of current MMEJ research is to identify novel factors that regulate or directly catalyze MMEJ, to define the genetic and biochemical underpinnings by which they function, and to test their value as potential druggable targets. We have identified RTEL1 as a novel factor that is required for efficient MMEJ. RTEL1 encodes an essential DEAH helicase that disassembles various DNA structures including a key recombination intermediate, the displacement loop (D-loop). We hypothesize that RTEL1 promotes MMEJ by dissociating D-loop structures that otherwise compete with MMEJ. Our model explains several enigmatic observations regarding the inhibitory roles of HR factors in MMEJ and provides a mechanistic framework for understanding the pathology of RTEL1-associated diseases. We will test this innovative idea using a combination of molecular genetics and in vitro biochemistry. This project will better define the mechanism of MMEJ and its regulation, and may reveal factors that can be targeted to treat environmentally induced diseases such as cancer and neurological disorders. As such, our work will exert a strong impact on environmental health research.