Suppression of translocations by RecQ-like DNA helicases

项目摘要 某些具有极端癌症风险的人类遗传疾病，如布鲁姆综合征 和Werner综合征，与RecQ的DNA解旋酶突变有关 一家人。缺乏Sgs1的酿酒酵母突变体，唯一的RecQ- 这种酵母中的相关DNA解旋酶，已经被证明是一些很好的模型系统 Bloom‘s综合征和Werner综合征的细胞表型，尤其是 它们的超重组表型。尽管总积累率- 染色体重排仅在SGS1中轻度升高？变种人，它是 最近的研究表明，缺乏SGS1的细胞对经历复杂的， 高度分化基因中小区域同源驱动的反复易位 (60%-65%的同一性)。尽管SGS1和错配修复蛋白是 相似但不相同(同源)序列之间的重组，只有SGS1是 抑制这些复杂和反复的易位所需的。这个 这项建议的目的是研究染色体内和染色体间的重组 在缺少SGS1的情况下导致同源易位的机制。这个 这项研究的具体目的是：(1)确定基因结构和 染色体环境控制同源同源基因驱动的速率和结构 SGS1中的易位？缺乏DNA损伤检查点传感器或染色质的突变体 装配系数。这将通过修改位置、方向和复制来实现 易位靶点的数量以及同源区段距离和DNA序列 身份。(2)阐明DNA损伤检查点的差别化要求 SGS1中抑制和形成复发性易位的成分？ 变种人。(3)研究功能结构域的作用和已知的物理相互作用 SGS1在抑制同源易位中的作用。(4)确定工作人员的能力 5种取代SGS1的人RecQ样DNA解旋酶抑制肿瘤生长的研究 同源基因驱动的易位。SGS1将被人类RecQ的cDNA取代 同源物，其中一些已在酵母中成功表达并抑制 SGS1的某些方面？突变表型。这些研究将提供机械论 对RecQ解旋酶在维持基因组完整性和意志方面的作用的见解 阐明了导致总染色体重排的一般机制， 尤其是基因易位，这往往与人类癌症有关。项目叙事 基因组不稳定是大多数癌症的一个标志，但其原因仍不清楚。 拟议中的研究将为DNA解离的作用提供机械性的见解 酶在维持基因组完整性方面的作用，并将有助于阐明 导致染色体重排，特别是基因易位的机制， 它们通常与人类癌症和染色体断裂综合征有关。

Project Summary Certain human genetic disorders with extreme cancer risk, such as Bloom's syndrome and Werner syndrome, are associated with mutations in DNA helicases of the RecQ family. Mutants of the yeast Saccharomyces cerevisiae that lack Sgs1, the only RecQ- related DNA helicase in this yeast, have proven to be excellent model systems for some cellular phenotypes of the Bloom's and Werner syndromes, especially with respect to their hyperrecombination phenotype. Although rates of accumulating gross- chromosomal rearrangements are only moderately elevated in sgs1? mutants, it was recently shown that cells lacking Sgs1 are uniquely susceptible to undergoing complex, recurring translocations driven by small regions of homology in highly diverged genes (60-65 % identity). Although Sgs1 and mismatch repair proteins are inhibitors of recombination between similar but nonidentical (homeologous) sequences, only Sgs1 is required for the suppression of these complex and recurring translocations. The objective of this proposal is to study the intra- and interchromosomal recombination mechanisms that cause homeology-driven translocations in the absence of Sgs1. The specific aims of this study are to: (1) Determine the extent to which gene structure and chromosome environment control the rate and structure of homeology-driven translocations in sgs1? mutants lacking DNA damage checkpoint sensors or chromatin assembly factors. This will be achieved by modifying location, orientation and copy number of translocation targets as well as homology block distance and DNA sequence identity. (2) Elucidate the differential requirement of DNA-damage checkpoint components for the suppression and formation of recurring translocations in sgs1? mutants. (3) Examine the role of functional domains and known physical interactions of Sgs1 in the inhibition of homeology-driven translocations. (4) Determine the ability of the five human RecQ-like DNA helicases to substitute for Sgs1 in the suppression of homeology-driven translocations. SGS1 will be replaced with cDNAs of human RecQ homologs, some of which have been successfully expressed in yeast and suppress some aspects of the sgs1? mutant phenotype. These studies will provide mechanistic insights into the role of RecQ helicases in the maintenance of genome integrity and will shed light on the general mechanisms leading to gross-chromosomal rearrangements, especially gene translocations, which are often associated with human cancers. Project Narrative The causes of genome instablity, which is a hallmark of most cancers, are still unclear. The proposed studies will provide mechanistic insights into the role of DNA unwinding enzymes in the maintenance of genome integrity and will shed light on the general mechanisms leading to chromosomal rearrangements, especially gene translocations, which are often associated with human cancers and chromosome breakage syndromes.