Regulation of Ionizing Radiation Induced DNA Damage Response

描述(由申请人提供)： 电离辐射诱导DNA双链断裂，激活ATM/ATR激酶启动的信号级联反应。损伤信号停止细胞周期进程，并为DNA损伤修复提供足够的时间。在这里，我们已经确定了一个重要的调节因子，RNF8(Ring Finger Protein 8)，它参与了DNA损伤反应的激活。DNA损伤后，RNF8的FHA结构域识别磷酸化的MDC1，它是DNA损伤反应中组蛋白H_2AX的结合伙伴，以RNF8为靶点。组蛋白H2AX是一种支架蛋白，它将DNA损伤反应蛋白保留在DNA损伤部位。由于RNF8是一种E3泛素连接酶，我们发现RNF8在DNA损伤后控制组蛋白H_2AX泛素化。依赖于RNF8的H2 AX泛素化可能调节下游的53BP1(P53结合蛋白1)和BRCA1(乳腺癌易感基因1)易位到DNA损伤部位。BRCA1和53BP1都是ATM/ATR激酶的下游靶点，也是重要的肿瘤抑制因子。此外，我们还培育了RNF8基因敲除小鼠。RNF8基因缺失的小鼠是可行的。但雄性RNF8-/-小鼠是不育的。RNF8-/-小鼠对电离辐射过敏。这些表型与组蛋白H_2AX和mdc1基因敲除小鼠非常相似。因此，根据我们的初步研究，我们假设RNF8在激活DNA损伤反应中发挥主要作用，并参与肿瘤预防。我们建议进行以下实验来检验我们的假设。目的：探讨依赖RNF8的组蛋白泛素化在DNA损伤反应中的作用。目的：研究RNF8在DNA损伤后组蛋白甲基化中的作用。目的：探讨RNF8在肿瘤抑制中的作用。综上所述，我们提出的研究不仅将对DNA损伤反应的激活机制提供深入的见解，而且有助于我们对维持基因组完整性和肿瘤预防的理解。

DESCRIPTION (provided by applicant): Ionizing radiation induces DNA double stand breaks, which activates a signal cascade initiated by ATM/ATR kinases. The damage signals stop the cell cycle progression and allow enough time for DNA damage repair. Here, we have identified an important regulator, RNF8 (Ring Finger protein 8) that participates in the activation of DNA damage response. Following DNA damage, the FHA domain of RNF8 recognizes phosphorylated MDC1, a binding partner of histone H2AX in DNA damage response, which targets RNF8 to DNA damage sites. Histone H2AX is a scaffold protein that retains DNA damage response proteins at the DNA damage sites. Since RNF8 is an E3 ubiquitin ligase, we have found that RNF8 controls histone H2AX ubiquitination following DNA damage. RNF8-dependent H2AX ubiquitination may regulate downstream 53BP1 (p53 Binding Protein 1) and BRCA1 (Breast Cancer Susceptibility Gene 1) translocation to DNA damage sites. Both BRCA1 and 53BP1 are not only downstream targets of ATM/ATR kinases, but also important tumor suppressors. Moreover, we have generated RNF8 knock-out mice. The RNF8 null mice are viable. But male RNF8 -/- mice are sterile. RNF8 -/- mice are hypersensitive to ionizing radiation. These phenotypes are very similar to those of histone H2AX and MDC1 knock-out mice. Thus, based on our preliminary studies, we hypothesize that RNF8 plays a major role in activation of DNA damage response and participates in tumor prevention. We propose following experiments to examine our hypotheses. Aim1: To investigate the role of RNF8-dependent histone ubiquitination in DNA damage response. Aim2: To study the role of RNF8 in histone methylation in response to DNA damage. Aim3: To examine the role of RNF8 in tumor suppression. In summary, our proposed studies will not only provide insights into the mechanisms of the activation of DNA damage response, but also contribute to our understanding of the maintenance of genomic integrity and tumor prevention.