SPOP通过泛素化53BP1促进同源重组修复的分子机制研究

DNA损伤修复是维持基因组稳定的重要生命过程。53BP1是DNA损伤时NHEJ修复的关键蛋白。SPOP是一个存在高频突变的E3泛素连接酶，具有促进HR修复的功能，但其作用机制仍不清楚。我们的预实验发现：SPOP可与53BP1相互作用，促进53BP1的非降解型泛素化；泛素特异识别蛋白NPL4可与53BP1互作；SPOP突变细胞中53BP1在DNA损伤位点的停留时间更长，含有更多的双链断裂点，对PARP抑制剂更敏感。本课题将进一步运用免疫荧光、免疫共沉淀、细胞生物学及动物模型等实验方法，从分子、细胞和模式动物等多个层次深入阐述SPOP通过泛素化53BP1促使其被VCP-NPL4复合物识别并带离DNA双链断裂位点，从而促进同源重组修复的分子机制，探讨在SPOP突变的肿瘤中使用PARP抑制剂的抑癌效果，为SPOP突变型肿瘤的精准治疗提供重要的理论依据及治疗思路。

DNA damage repair is a very important life process to maintain genome stability. 53BP1 is the key protein for NHEJ repair during DNA damage response. SPOP, an E3 ubiquitin ligase with high frequency mutation, possesses the function of promoting HR repair, but the underling mechanism is still unclear. In our preliminary work, we found that SPOP interacts with 53BP1 and promotes the non-degradable ubiquitination of 53BP1. The ubiquitin-specific recognition protein NPL4 also specifically interacts with 53BP1. In SPOP mutant cells, 53BP1 has a longer residence time at DSB site and contains more double-chain breaking points, and cells are more sensitive to PARP inhibitors. By using immunofluorescence, immunoprecipitation, cell biology and animal models, this project will further study the mechanism by which SPOP ubiquitylates 53BP1, promotes the recognition and extraction of 53BP1 by VCP-NPL4 complex from DNA double-strand break sites, so as to promote homologous recombination repair. This project will also investigate the anticancer effect of PARP inhibitors in SPOP mutated tumors. In brief, this study will provide important theoretical basis and treatment ideas for the precise treatment of SPOP mutant tumors.