Chromatin Regulation of Double-Strand Break Repair

DNA修复和DNA损伤检查点对肿瘤抑制很重要，也是至关重要的 肿瘤耐受放射和化疗药物的决定因素。DNA双链断裂(DSB) 是由遗传毒性化学物质和电离辐射产生的，并在DNA过程中自发产生 复制。DSB通过非同源末端连接(NHEJ)和同源重组修复 (HR)。DSB发生在染色质的背景下，染色质的变化在 DNA修复和检查点蛋白在损伤部位的招募。拟议的研究旨在 确定染色质修饰和重塑在蛋白质募集到DSB中的作用，以及在 酿酒酵母DSB修复结果的调控。我们的中心假设是 DSB修复效率和结果是通过修复蛋白的综合作用来调节的， 检查点蛋白和染色质动力学。我们将通过追求三个具体目标来检验这一假设 集中在(1)染色质变化在DSB的修复和检查点蛋白募集中的作用；(2) 确定在HR期间DSB部位和供体部位的染色质变化；以及(3)确定染色质如何 调节DSB修复。与组蛋白H_2A的磷酸化一样，我们发现核小体置换 在及时地将修复蛋白招募到DSB中起作用。这些染色质和其他染色质的作用 DSB的蛋白质募集、DSB修复的调节和检查点激活的变化将是 调查过了。这些研究将阐明染色质改变如何调节细胞对DSB的反应和 从而确定DSB损伤的遗传后果。拟议的研究之所以相关，是因为 染色质修饰、DSB修复和检查点反应从酵母到人都是保守的。这个 研究意义重大，因为它们将揭示DSB修复的新调节机制，从而确定 在癌症放射和化疗中开发新的靶点。

DMA repair and DNA damage checkpoints are important for tumor suppression, and are critical determinants of tumor resistance to radiation and chemotherapeutics. DNA double-strand breaks (DSBs) are produced by genotoxic chemicals and ionizing radiation, and arise spontaneously during DNA replication. DSBs are repaired by non-homologous end-joining (NHEJ) and homologous recombination (HR). DSBs occur in the context of chromatin, and chromatin alterations play important roles in the recruitment of DNA repair and checkpoint proteins to damage sites. The proposed studies are designed to determine the roles of chromatin modification and remodeling in protein recruitment to DSBs, and in the regulation of DSB repair outcome in the yeast Saccharomyces cerevisiae. Our central hypothesis is that DSB repair efficiency and outcome are regulated through the integrated actions of repair proteins, checkpoint proteins, and chromatin dynamics. We will test this hypothesis by pursuing three Specific Aims focused on (1) the roles of chromatin changes in recruitment of repair and checkpoint proteins to DSBs; (2) defining chromatin changes at a DSB site and a donor locus during HR; and (3) determining how chromatin regulates DSB repair. As with phosphorylation of histone H2A, we found that nucleosome displacement plays a role in the timely recruitment of repair proteins to DSBs. The roles of these and other chromatin alterations in protein recruitment to DSBs, regulation of DSB repair, and checkpoint activation will be investigated. These studies will clarify how chromatin alterations regulate cellular responses to DSBs and thereby determine the genetic consequences of DSB damage. The proposed studies are relevant because chromatin modifications, DSB repair, and checkpoint responses are conserved from yeast to man. The studies are significant because they will reveal new regulatory mechanisms in DSB repair, and thus identify new targets to exploit in cancer radio- and chemotherapy.