“Parthanatos”是由PARP1过度活化引发的、凋亡诱导因子AIF介导的程序性细胞死亡，是再灌注损伤的主要病理因素。AIF不是核酸酶，如何引发DNA降解的分子机制长期未得到解决。近期有研究报道具核酸酶属性的MIF依赖AIF入核后可导致DNA降解，但作用机制缺乏合理解释。申请人前期研究工作发现，AIF与双链断裂标志蛋白H2AX相互作用加剧了DNA双链断裂损伤程度；同时MIF与H2AX也存在特异性相互作用。因此本项目研究将1）证明AIF与H2AX结合阻断了DNA双链断裂（DSBs）修复机器的招募，抑制了断裂的修复；2）证明MIF通过与AIF的作用靶向基因组DSBs位点，将修复产生的3’端突出单链DNA作为为底物进行降解；3）利用ChIP-Seq和DSB end-Seq技术，在全基因组水平分析MIF作用位点与DSBs位点的相关性。研究结果将揭示parthanatos信号的关键分子机制。

Parthanatos, one of programmed cell death modalities, is triggered by hyperactivation of PARP1, mediated by apoptosis inducing factor (AIF), and linked to diseases caused by ischemia reperfusion injury. AIF has no nuclease property, thus, how AIF induce DNA fragmentation remains as a long-lasting enigma. Recently, MIF has been documented as to be translocated with AIF into nucleus. MIF possesses nuclease activity, which acts on single strand DNA. However, the precise mechanism how AIF and MIF induce DNA fragmentation is still elusive. Our preliminary data shows that the interaction of AIF and H2AX blocked the recruitment of DSB DNA repair proteins to the latter, leading to impaired DSB repair; meanwhile, we observed the interaction of MIF with AIF/H2AX complex. Thus, in this proposed study, we will 1) verify that the interaction of AIF with H2AX competitively blocked the docking of DSB repair proteins to H2AX, causing failure of DSB repair; 2) demonstrate that once translocated in nucleus through complexing with AIF, MIF also targets to H2AX mediated by AIF/H2AX interaction, where MIF acts on the intermediates of DSB repair 3’ ssDNA retention, consequently, the broken genome remains fragmented; 3) analyze the correspondence of the recruitment sites of MIF and the DSBs sites by utilizing ChIP-seq and DSB end-seq. The proposed research will document a key molecular mechanism of parthanatos signal pathway.