DNA聚合酶zeta（Pol ζ）维持基因组稳定性的机制研究

It is extremely important to maintain the integrity of the genomic DNA as the carrier of genetic information. Unfortunately, our DNA is continuously insulted by external and internal factors such as ionizing radiation, UV light, reactive oxygen species generated from normal metabolism. If the DNA damages left unrepaired, they can lead to the occurrence of different diseases including cancer. Our body have developed a series of sophisticated mechanisms to handle these DNA lesions at extremely high efficiencies. DNA polymerases are essential for the maintenance of genomic stability. There are 15 different DNA polymerases encoded by the mammalian genomes, which are specialized for the replication, repair or tolerance of DNA damages. DNA polymerase zeta (Pol zeta) is one of the most important polymerases for DNA lesion repair/tolerance. A handful of evidence indicated the participation of Pol zeta in the post-invasion DNA synthesis of DNA homologous recombination, translesion DNA synthesis (TLS), and the repair/tolerance of DNA inter-strand crosslinks (ICLs). All of these pathways are essential for the healthiness of genomic DNA. In this proposal, the detailed mechanism of Pol zeta in these three different aspects of DNA metabolism will be explored in a biochemical approach. The obtained information would be valuable for understanding the role of Pol zeta in DNA mutagenesis, cancer development, and occurrence of chemotherapy resistance.

保持基因组DNA的完整性和稳定性对于细胞的存活和正常生理活动的进行具有重要意义。但是它时刻面临来自于生物体内部或外部的危害而不断出现损伤，进而导致细胞死亡或癌变等严重后果。DNA聚合酶对于维持基因组DNA稳定性至关重要。真核生物中已知的15种DNA聚合酶参与基因组DNA的复制与DNA损伤的修复。在负责DNA损伤修复的DNA聚合酶中，DNA聚合酶zeta (Pol zeta) 是相对研究较少但却具有重要的理论和临床意义的一种。近年来的研究表明Pol zeta 参与到多个对于维持基因组稳定性和防止疾病发生极其重要的生理过程，但具体机制还很不清楚。本项目将利用生物化学方法对Pol zeta 在同源重组单链侵入后的DNA合成，跨损伤DNA合成，以及DNA链间交联修复通路中的功能进行鉴定。所获结果将对理解与Pol zeta 相关的DNA突变、癌症发生、化疗抗药性的产生及临床应对方案提供重要理论依据。

维持DNA作为遗传信息携带者的分子结构完整性和稳定性对于细胞的存活和正常生理活动的进行具有重要意义。以DNA聚合酶zeta（Pol ζ）为代表的跨损伤DNA聚合酶对于维持基因组DNA的稳定性至关重要。本项目研究了DNA聚合酶zeta（Pol ζ）在维持基因组稳定性中所发挥的作用，并对其生化机制进行了探究。首先，本项目研究发现Pol ζ在DNA同源重组底物上相比于其它测试的DNA聚合酶具有相对更高的活性，这一结果是Pol ζ参与同源重组DNA合成的有利证据。本项目随后研究了Pol ζ与其它DNA聚合酶（如Pol δ）在跨损伤DNA合成中的转换，结果显示Pol ζ与Pol δ可协同作用克服DNA损伤的阻碍，完成高效的DNA合成。本项目还在人结直肠癌细胞系HCT116中进行了REV1及Pol ζ关键亚基（REV3L和REV7）的敲除，随后用顺铂处理细胞形成DNA链接交联（ICL）。上述基因敲除后，HCT116细胞对顺铂的敏感性大大增加，且细胞表现出DNA损伤积聚和细胞周期的阻滞。这部分结果表明，Pol ζ在DNA链间交联修复中起重要作用，是临床中导致铂类化疗药物耐药的重要因素之一。综上所述，本项目利用生物化学方法对Pol ζ 在同源重组单链侵入后的DNA合成，跨损伤DNA合成，以及DNA链间交联修复通路中的功能进行了研究，所获结果将对理解与Pol  相关的DNA突变、癌症发生、化疗抗药性的产生及临床应对方案具有重要意义。