Investigation of xrcc5 Mutant Mice

基因组不稳定是癌症的主要原因，也被认为是衰老的主要原因。编码KU80蛋白的基因XRCC5通过修复DNA中的双链断裂(DSB)和封顶染色体末端来维持基因组的稳定性。Ku80基因缺失的小鼠由于在可变(多样性)连接重组过程中发生的DSB修复缺陷而出现免疫缺陷，来自ku80突变小鼠的细胞对电离辐射和活性氧物种高度敏感。此外，这些细胞表现出包括端粒融合在内的细胞遗传学异常。Ku80突变小鼠在各种组织中表现出与年龄相关的早期变化，在对照组小鼠中也观察到了这些变化；因此，Ku80可能对正常的衰老过程很重要。这些变化包括生长板关闭、骨质减少、皮肤和毛囊萎缩、肝脏退化过程和寿命缩短。早期死亡至少部分是由于年龄相关疾病、败血症和癌症的早期发病。尽管ku80突变小鼠的癌症发病较早，但总的发病率很低。有趣的是，肿瘤抑制蛋白P53的缺失大大增加了患淋巴瘤的风险，这表明Ku80也是一种肿瘤抑制蛋白。Ku80在维持基因组稳定性中的生物学作用将在衰老和肿瘤发生过程中确定，这一提议的完成将显著影响我们对Ku80‘S在这些事件中的作用的理解。L：确定氧化损伤或端粒功能障碍引起的基因组不稳定性对ku80突变表型的影响。将比较ku80突变小鼠和对照小鼠的基因突变的开始和谱系。为了确定氧化损伤的影响，将对暴露在电离辐射中的ku80突变小鼠的DNA损伤进行测量，并通过过度表达清除氧自由基、过氧化氢酶和铜/锌超氧化物歧化酶的蛋白质来测量DNA损伤。为了研究端粒维持的影响，将对ku80-/-mtr-/-小鼠进行研究。2：确定一般基因组不稳定性对非淋巴组织中P53缺失的ku80突变小鼠肿瘤发生的影响。肿瘤抑制蛋白P53的作用将分析其对ku80突变小鼠肿瘤发生的影响，并在确定的小鼠模型中特别关注乳房组织。

Genomic instability is a major cause of cancer and believed to be a major contributor to aging. The gene Xrcc5, that codes for the protein, Ku80 is important for maintaining genomic stability by repairing double-strand breaks (DSBs) in DNA and by capping chromosomal ends. Mice deleted for Ku80 are immunodeficient due to defective repair of DSBs that occur during Variable (Diversity) Joining recombination and cells derived from ku80-mutant mice are hypersensitive to ionizing radiation and reactive oxygen species. In addition, these cells exhibit cytogenetic aberrations including telomeric fusions. ku80-mutant mice exhibit an early onset of age-related changes in a variety of tissues that are also observed in control mice; thus, Ku80 may be important for the normal aging process. These changes include growth plate closure, osteopenia, skin and follicular atrophy, degenerative processes in the liver and shortened life span. Early mortality was at least partly due to early onset of the age - specific diseases, sepsis and cancer. Even though onset of cancer is early for ku80-mutant mice, the total incidence is low. Interestingly, deletion of the tumor suppressor protein, p53, greatly increased the risk of lymphoma suggesting that Ku80 is also a tumor suppressor. The biological role of Ku80 in maintaining genomic stability will be determined during aging and oncogenesis and completion of this proposal will significantly impact our understanding of Ku80's role during these events. l: Determine the contribution genomic instability, induced by either oxidative damage or telomere dysfunction, has on the ku80-mutant phenotype. The onset and spectra of genetic mutations will be compared between ku80-mutant and control mice. To determine the impact of oxidative damage, DNA lesions will be measured in ku80- mutant mice after exposure to ionizing radiation and by overexpressing proteins that eliminate oxygen radicals, catalase and Cu/Zn-superoxide dismutase. To investigate the impact of telomere maintenance, ku80-/- mTR-/- mice will be investigated. 2: Determine the impact general genomic instability has on oncogenesis in ku80-mutant mice that are deleted for p53 in nonlymphoid tissue. The role of the tumor suppression protein, p53, will be analyzed for its impact on oncogenesis in ku80-mutant mice with specific attention given to mammary tissue in a defined mouse model.