DNA聚合酶eta调控依托泊苷诱发损伤修复的分子机理与肿瘤耐药

DNA polymerase η plays an important role in genome mutagenesis and chemotherapeutic drug resistance. In addition to its role in translesion DNA synthesis (TLS), we discovered surprisingly that Polη is involved in non-homologous end joining (NHEJ) pathway and regulates cellular sensitivity to chemotherapeutic drug etoposide. Evidence has shown that double-strand breaks (DSBs) are the main type of damages result from etoposide, but it is remains indistinct about the detailed function and mechanism of Polη in DSB repair. We found that Polη is recruited to DSBs and promotes NHEJ repair. Loss of Polη sensitizes cells to etoposide treatment and restrains DNA replication rate. By integrating multiple cellular, biochemical and molecular techniques and mouse models, this project aims at exploring the mechanism of Polη in regulating etoposide-induced damage repair as well as the novel function of Polη in DSB repair, revealing the correlation of NHEJ and TLS function of Polη, and determining the effect of Polη in etoposide resistance of cancer. Unveiling of the molecular mechanism of Polη in regulating etoposide-induced damage repair will provide important insights into the understanding of carcinogenesis, and supply scientific basis for cancer prevention and treatment.

DNA聚合酶Polη在基因组变异和肿瘤化疗耐药性产生中发挥重要作用，除了跨损伤DNA合成（TLS）通路，我们最近意外发现Polη还参与非同源末端连接（NHEJ）通路，调控细胞对化疗药物依托泊苷的敏感性。已知依托泊苷主要是通过造成DNA双链断裂（DSB）诱发癌细胞凋亡，目前关于Polη在DSB修复中的详细功能和作用机制还很不清楚。前期结果表明Polη能够被招募到DSB损伤位点，促进NHEJ修复，缺失Polη导致细胞对依托泊苷敏感性增强和DNA复制速率降低。本项目拟整合多种生化分子和细胞生物学技术，结合小鼠模型，深入研究Polη调控依托泊苷诱发损伤修复的作用机制，揭示Polη在DSB修复中的新功能；分析Polη在NHEJ和TLS通路中功能的相关性，丰富DNA损伤应答网络；探讨Polη对依托泊苷治疗的影响，阐明其与肿瘤化疗耐药的关联，为深入理解癌症发生和进行肿瘤防治提供重要理论基础和科学依据。

DNA聚合酶eta（Polη）属于真核Y家族DNA聚合酶，它在跨损伤合成（TLS）通路和基因组突变发生过程中发挥重要作用。最近，已有一些TLS聚合酶被报道参与DNA双链断裂（DSB）损伤修复。但是，Polη是否参与DSB修复尚未可知。在本研究中，我们发现Polη能够募集到依托泊苷（ETO）诱导的DSB损伤位点，缺失Polη导致细胞对ETO敏感性显著增加。有趣的是，Polη以一种不依赖自身DNA聚合酶活性的方式促进非同源末端连接（NHEJ）的修复效率。我们还发现Kap1与Polη结合，缺失Kap1导致Polη和Rad18到ETO诱发损伤位点的招募明显降低。同时，过表达Kap1并不能恢复Rad18缺失细胞中降低的Polη到ETO损伤位点的招募比例。此外，我们发现Kap1与Rad18的结合依赖Polη，而缺失Kap1则导致Rad18/Polη的结合明显减弱，说明Kap1与Rad18、Polη形成蛋白三聚体，起到稳定Rad18/Polη结合的作用。我们的发现阐明了Kap1能够通过促进Rad18zh招募和稳定Rad18/Polη结合的两种方式调控Polη修复ETO诱发DSB的功能。