Luo Kuntian, Li Lei, Li Yunhui, Wu Chenming, Yin Yujiao, Chen Yuping, Deng Min, Nowsheen Somaira, Yuan Jian, Lou Zhenkun
Research Center for Translational Medicine, East Hospital, Tongji University School of Medicine, Shanghai 200120, China.
Key Laboratory of Arrhythmias of the Ministry of Education of China, East Hospital, Tongji University School of Medicine, Shanghai 200120, China.
Genes Dev. 2016 Dec 1;30(23):2581-2595. doi: 10.1101/gad.289439.116. Epub 2016 Dec 9.
Homologous recombination (HR) is one of the major DNA double-strand break (DSB) repair pathways in mammalian cells. Defects in HR trigger genomic instability and result in cancer predisposition. The defining step of HR is homologous strand exchange directed by the protein RAD51, which is recruited to DSBs by BRCA2. However, the regulation of the BRCA2-RAD51 axis remains unclear. Here we report that ubiquitination of RAD51 hinders RAD51-BRCA2 interaction, while deubiquitination of RAD51 facilitates RAD51-BRCA2 binding and RAD51 recruitment and thus is critical for proper HR. Mechanistically, in response to DNA damage, the deubiquitinase UCHL3 is phosphorylated and activated by ATM. UCHL3, in turn, deubiquitinates RAD51 and promotes the binding between RAD51 and BRCA2. Overexpression of UCHL3 renders breast cancer cells resistant to radiation and chemotherapy, while depletion of UCHL3 sensitizes cells to these treatments, suggesting a determinant role of UCHL3 in cancer therapy. Overall, we identify UCHL3 as a novel regulator of DNA repair and reveal a model in which a phosphorylation-deubiquitination cascade dynamically regulates the BRCA2-RAD51 pathway.
同源重组（HR）是哺乳动物细胞中主要的DNA双链断裂（DSB）修复途径之一。HR缺陷会引发基因组不稳定并导致癌症易感性。HR的决定性步骤是由蛋白质RAD51指导的同源链交换，RAD51由BRCA2招募至DSB处。然而，BRCA2-RAD51轴的调控机制仍不清楚。在此，我们报告RAD51的泛素化会阻碍RAD51与BRCA2的相互作用，而RAD51的去泛素化则促进RAD51与BRCA2的结合以及RAD51的招募，因此对正确的HR至关重要。从机制上讲，响应DNA损伤时，去泛素化酶UCHL3会被ATM磷酸化并激活。UCHL3继而使RAD51去泛素化，并促进RAD51与BRCA2之间的结合。UCHL3的过表达使乳腺癌细胞对放疗和化疗产生抗性，而UCHL3的缺失则使细胞对这些治疗敏感，这表明UCHL3在癌症治疗中起决定性作用。总体而言，我们将UCHL3鉴定为DNA修复的新型调节因子，并揭示了一种磷酸化-去泛素化级联反应动态调节BRCA2-RAD51途径的模型。
