SPOP泛素化p62促电离辐射诱导DNA双链断裂的同源重组修复机制研究

电离辐射诱导DNA双链断裂可通过同源重组（HR）进行修复。研究表明SPOP缺失导致HR修复抑制，其分子机制不明。既往研究p62抑制HR修复是通过抑制RNF168对组蛋白泛素化修饰及通过介导泛素化降解HR关键分子Rad51和FLNA。我们研究发现：1)p62与SPOP之间有蛋白相互作用，且存在共定位，p62存在SPOP特异性结合底物的序列即SBC基序；2)SPOP与p62表达呈负相关，SPOP调控p62的蛋白稳定性；3)敲低p62可回复敲低SPOP引起的HR修复效率下降。因此我们推断：p62是SPOP的泛素化底物；SPOP缺失导致p62不能泛素化降解,从而核内聚集，进而通过p62介导的RAD51和FLNA蛋白泛素化降解和（或）通过p62抑制RNF168泛素化组蛋白，最终抑制HR修复？本课题拟通过体内外实验，揭示SPOP泛素化p62促电离辐射诱导DNA双链断裂的同源重组修复分子机制。

DNA double-strand breaks (DSBs) induced by ionizing radiation (IR) are repaired through homologous recombination (HR), which is a multi-factor process. Previous study showed SPOP deletion suppressed HR repair, but the molecular mechanisms are unknown. Previous study also showed that p62 suppressed HR repair by inhibiting ubiquitination modification of histone by RNF168 and ubiquitination degradation of Rad51 and FLNA. Rad51 and FLNA are key molecules of HR. Our previous study found: 1) SPOP can interacts with p62 and both are co-located. P62 has the sequence of SPOP specific binding substrate, which is the SBC sequence. 2) SPOP has a negative correlation with the expression of p62 and regulates the stability of p62 protein; 3) Knockdown of p62 can restore the reduction of HR repair efficiency caused by knockdown of SPOP. Taken together, p62 is the ubiquitination substrate of SPOP; SPOP deletion led to the loss of its ability to ubiquitination degradation of p62 and promotes p62 nuclear aggregation, which induces ubiquitination degradation of RAD51 and FLNA and/or inhibition of ubiquitination histone of RNF168 by p62. Finally, HR repair is inhibited. This study explores the molecular mechanism of HR repair of IR-induced DNA double strand breaks by SPOP ubiquitination p62 in vitro and in vivo.