The Role of the Mre11 Complex in Heat-radiosensitization

描述（由申请人提供）：几项III期临床试验已经验证了使用热疗作为放射治疗的辅助治疗。 高温使哺乳动物细胞对电离辐射敏感。 因此，如果能更好地理解热辐射增敏的分子机制，在临床中使用热的潜在益处可能会最大化。 辐射诱导DNA双链断裂（DSB）的形成，并且热辐射增敏被认为是由热抑制辐射诱导的DSB的修复引起的。 通常，辐射诱导的DSB修复被认为通过两种途径发生：非同源末端连接（NHEJ）和同源重组（HR）。 Mre11复合物被认为在这两种途径中发挥作用。 我们的初步数据表明，高温诱导改变Mrell，RadSO和Nbsl，蛋白质组成的Mre11复合物。 我们还表明，热诱导这些蛋白质从细胞核到细胞质的易位。 热诱导的改变，或重新分配的Mre 11复合物的组成部分可能会导致DSB修复效率的降低和增强辐射诱导的细胞杀伤。 我们将测试的假设，热辐射增敏是由热诱导的改变，或重新分配的Mre 11 DSB修复复合物的蛋白质。 我们将确定Mre 11和Rad50在热辐射增敏中的作用，并确定这些蛋白质的改变是否会导致细胞暴露于中等温度（41.5 ℃）高温治疗后DSB修复和热辐射增敏效率的抑制或降低。 使用Western印迹和共聚焦显微镜，我们将表征热诱导的热损伤，或重新定位的Mre 11，RadSO，和Nbsl，并试图确定这些改变发生的机制。 我们还将使用沉默RNA（siRNA）靶向技术或缺乏特定NHEJ或HR蛋白的条件突变体来确定HR在热辐射增敏中的作用。

DESCRIPTION (provided by applicant): Several phase III clinical trials have validated the use of hyperthermia as an adjuvant to radiation therapy. Hyperthermia sensitizes mammalian cells to ionizing radiation. Therefore, the potential benefit of using heat in the clinic may be maximized if the molecular mechanisms for heat-radiosensitization are better understood. Radiation induces the formation of DNA double strand breaks (DSBs), and thermal radiosensitization is believed to be caused by an inhibition of repair of radiation-induced DSBs by heat. Normally, radiationinduced DSB repair is believed to occur via two pathways: non-homologous end-joining (NHEJ) and homologous recombination (HR). The Mre11 complex has been implicated to function in both of these pathways. Our preliminary data suggest that hyperthermia induces alterations to Mrell, RadSO and Nbsl, the proteins comprising the Mre11 complex. We have also shown that heat induces the translocation of these proteins from the nucleus to the cytoplasm. Heat-induced alterations to, or redistribution of the components of the Mre11 complex could result in a decrease in DSB repair efficiency and potentiation of radiationinduced cell killing. We will test the-hypothesis that heat-radiosensitization is caused by heat-induced alterations to, or redistribution of proteins of the Mre11 DSB repair complex. We will determine the role of Mre11 and Rad50 in heat-radiosensitization, and determine whether alterations of these proteins lead to an inhibition or decrease in the efficiency of DSB repair and heat-radiosensitization after cells are exposed to moderate temperature (41.5¿C) hyperthermia treatments. Using Western blotting and confocal microscopy, we will characterize heat-induced thermal damage to, or relocalization of Mre11, RadSO, and Nbsl and attempt to identify the mechanisms by which these alterations occur. We will also determine the role of HR in heat-radiosensitization using silencing RNA (siRNA) targeting technology or conditional mutants deficient in specific NHEJ or HR proteins.