Investigation of xrcc5 Mutant Mice

基因组不稳定是癌症的主要原因，被认为是衰老的主要原因。编码蛋白质Ku80的基因Xrcc5对于通过修复DNA中的双链断裂（dsb）和覆盖染色体末端来维持基因组的稳定性很重要。Ku80基因缺失的小鼠由于在可变（多样性）连接重组过程中dsb的修复缺陷而产生免疫缺陷，Ku80突变小鼠衍生的细胞对电离辐射和活性氧敏感。此外，这些细胞表现出包括端粒融合在内的细胞遗传畸变。ku80突变小鼠在多种组织中表现出与年龄相关的早期变化，这在对照小鼠中也观察到；因此，Ku80可能对正常的老化过程很重要。这些变化包括生长板闭合、骨质减少、皮肤和卵泡萎缩、肝脏退行性过程和寿命缩短。早期死亡至少部分是由于年龄特异性疾病，败血症和癌症的早期发作。尽管ku80突变小鼠的癌症发病较早，但总发病率较低。有趣的是，肿瘤抑制蛋白p53的缺失大大增加了淋巴瘤的风险，这表明Ku80也是一种肿瘤抑制因子。Ku80在维持基因组稳定性方面的生物学作用将在衰老和肿瘤发生过程中确定，这一建议的完成将显著影响我们对Ku80在这些事件中的作用的理解。l：确定由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ku80突变小鼠与对照小鼠的基因突变的开始和谱进行比较。为了确定氧化损伤的影响，ku80突变小鼠暴露于电离辐射后，通过过表达消除氧自由基、过氧化氢酶和Cu/ zn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，我们将对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突变小鼠的肿瘤发生的影响。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腺组织。

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.