Cooperative roles for Atm and Hus1 in genome maintenance

项目总结 共济失调-毛细血管扩张症是一种基因组不稳定综合征，其中DNA突变破坏 检查点蛋白ATM导致神经退行性变、癌症易感性、不孕不育和免疫 功能障碍。ATM在细胞对双链DNA断裂(DSB)的反应中发挥着核心作用， 而涉及相关检查点蛋白ATR的第二条途径响应复制应激和 巨大的DNA损伤以及DSB。这些通路之间的功能重叠程度为 不完全了解的部分原因是ATR途径的组成部分，其中也包括Chk1 和Rad9-Rad1-Hus1(911)复合体，是生存所必需的。该计划的长远目标 本提案中描述的研究是为了解决ATM和ATR通路之间的关系 并确定ATR通路的活性如何影响ATM时的疾病发病机制 有缺陷的。我们在小鼠中使用了Hus1等位基因系列来识别ATM之间的遗传交互作用 和ATR路径。当部分Hus1损伤合并时，观察到合成致死性 在ATM不足的情况下，建立两个主要部门之间必不可少的合作关系 哺乳动物DNA损伤检查点通路。尽管Hus1的表达严重减少 在ATM丢失的情况下是致命的，略高水平的Hus1表达产生了存活的小鼠 频率低于预期。在目标一中，将确定胚胎致死的基础。 通过胚胎的形态和组织学分析以及DNA损伤的检测 同时存在ATM和HUS1缺陷的培养细胞中的信号转导。此外，存活下来的小鼠 同时检测ATM和HUS1缺陷的是神经变性，这是一种突出的表型 共济失调--在ATM基因敲除小鼠中未观察到的毛细血管扩张患者。在目标二中， 我们将评估HUS1在ATM缺陷小鼠肿瘤发展中的作用。自动取款机 杂合子会增加人类患乳腺癌的风险，因此肿瘤的形成将 也可以在带有部分Hus1缺陷的杂合子ATM小鼠中进行检测。总而言之， 拟议的研究将澄清两种主要哺乳动物DNA损伤之间的关系 检查点途径和解决这些基因组维护机制的合作角色 在执行发育程序、防止神经退化和抑制 肿瘤发生学。相关性 共济失调-毛细血管扩张症是一种毁灭性的疾病，估计每40,000名新生儿中就有一名。这个 拟议中的研究将确定这种疾病的严重程度如何，这可能会有很大的差异 人与人之间，受一条相关途径的活动影响。这些研究还将澄清 负责维持基因组完整性的信令网络的组织，并可 为未来的翻译研究制作更准确的共济失调-毛细血管扩张症小鼠模型。

PROJECT SUMMARY Ataxia-Telangiectasia is a genomic instability syndrome in which mutations in the DNA damage checkpoint protein Atm cause neurodegeneration, cancer predisposition, infertility, and immune dysfunction. Atm plays a central role in cellular responses to double-stranded DNA breaks (DSB), while a second pathway involving the related checkpoint protein Atr responds to replication stress and bulky DNA lesions, as well as DSB. The extent of functional overlap between these pathways is incompletely understood in part because components of the Atr pathway, which also includes Chk1 and the Rad9-Rad1-Hus1 (911) complex, are essential for viability. The long-term objectives of the research described in this proposal are to resolve the relationship between the Atm and Atr pathways and to determine how the activity of the Atr pathway affects disease pathogenesis when Atm is defective. We employed a Hus1 allelic series in mice to identify genetic interactions between the Atm and Atr pathways. Synthetic lethality was observed when partial Hus1 impairment was combined with Atm deficiency, establishing an essential cooperative relationship between the two primary mammalian DNA damage checkpoint pathways. Although a severe reduction in Hus1 expression was lethal in combination with Atm loss, a slightly higher level of Hus1 expression yielded viable mice at less than expected frequency. In aim one, the basis for the embryonic lethality will be determined by morphological and histological analysis of embryos as well as by examination of DNA damage signaling in cultured cells with both Atm and Hus1 defects. In addition, surviving mice with simultaneous Atm and Hus1 defects will be tested for neurodegeneration, a prominent phenotype of Ataxia-Telangiectasia patients that is not observed in Atm knockout mice. In aim two, the impact of reduced Hus1 function on tumor development in Atm-deficient mice will be assessed. Atm heterozygosity confers an increased risk of breast cancer in humans, and therefore tumorigenesis will also be examined in heterozygous Atm mice with a partial Hus1 defect. Taken together, the proposed studies will clarify the relationship between two primary mammalian DNA damage checkpoint pathways and resolve the cooperative roles for these genome maintenance mechanisms in executing developmental programs, preventing neurodegeneration, and suppressing tumorigenesis. RELEVANCE Ataxia-Telangiectasia is a devastating disease with an estimated frequency of 1 in 40,000 births. The proposed research will determine how the severity of this disease, which can vary significantly between individuals, is affected by the activity of a related pathway. The studies also will clarify the organization of the signaling networks responsible for the maintenance of genomic integrity and may produce a more accurate mouse model for Ataxia-Telangiectasia for future translational studies.