MECHANISMS OF RDIATION RESPONSE AND ADP RIBOSE METABOLISM

这项提案的总体目标是调查 聚腺苷二磷酸核糖聚合酶(PARP)在细胞对电离反应中的作用 辐射损伤。从我们进行的实验中积累的证据 和其他人表明，尽管PARP似乎是 哺乳动物细胞中的G2检查点，它不是DNA的必需基因 DNA修复的复制或核苷酸切除途径。这些 研究结果支持细胞的辐射反应依赖于有效的 聚(ADP-核糖)代谢。我们假设这一水平和模式 激活的PARP的作用是电离辐射恢复的关键 对DNA的损害，以及正常调控系统中的扰动 过度DNA损伤导致的PARP水平和活性导致 细胞反应中细胞凋亡途径的增强。 尤文氏肉瘤(EWS)细胞作为主要实验模型系统 对于放射敏感性和高PARP水平，我们提出了一种实验性的 方法：1)研究PARP和PARP的转录调控 确定它是否因辐射暴露而改变，2)确定蛋白水解物 参与PARP基因产物周转的系统，以及3) 确定PARP-周转蛋白水解酶的参与和作用 对辐射诱导的DNA损伤和细胞凋亡的反应。 来自这些实验的数据将确定与 细胞对电离辐射的反应。一个重要的限制因素 在肿瘤治疗中放射治疗是固有的放射敏感性 肿瘤细胞的数量。了解辐射反应的机制， 尤其是那些促进肿瘤细胞凋亡的药物，将使 制定提高临床治愈率的策略。

The overall objective of this proposal is to investigate the role of poly(ADP-ribose) polymerase (PARP) in the cellular response to ionizing radiation injury. Evidence accumulated from experiments performed by us and others indicates that, although PARP appears to be an element in the G2 checkpoint in mammalian cells, it is not an essential gene for DNA replication or the nucleotide excision pathway for DNA repair. These findings support that the cellular radiation response rely on effective poly(ADP-ribose) metabolism. We hypothesize that the level and mode of action of activated PARP is critical for recovery from ionizing radiation damage to DNA, and that perturbations in the normal regulatory systems for PARP levels and activity by excessive DNA damage result in the potentiation of the apoptosis pathway in the cellular response. Using Ewing's sarcoma (EWS) cells as the primary experimental model system for radiosensitivity and high PARP levels, we propose an experimental approach designed to: 1) study the transcriptional regulation of PARP and determine if it is altered by radiation exposure, 2) identify proteolytic systems involved in the turnover of the PARP gene product, and 3) establish the participation and role of the PARP-turnover proteases in the response to radiation-induced DNA damage and apoptosis. Data from these experiments will identify molecular events associated with the cellular response to ionizing radiation. An important limiting factor in tumor treatment by radiation therapy is the intrinsic radiosensitivity of tumor cells. Understanding the mechanisms of radiation response, particularly those potentiating tumor cell apoptosis, will allow the development of strategies for improving the clinical therapeutic ratio.