P53蛋白二阶段磷酸化修饰在砷"致癌与治癌"双重作用中的机制研究

细胞在砷诱导DNA损伤反应中的命运抉择（增殖或凋亡）决定了砷是"致癌"还是"治癌"，而命运抉择的机制与P53蛋白二阶段磷酸化修饰及调控其转换的去磷酸化酶WIP1密切相关。已有研究显示砷诱导的DNA损伤可以激活P53，提示砷可能通过P53信号通路以P53蛋白二阶段磷酸化修饰机制决定细胞暴露的结局。然而，P53蛋白二阶段磷酸化修饰是否参与砷诱导的DNA损伤反应？不同的磷酸化修饰是否会导致不同的结局？调控WIP1是否可以成为砷治癌增敏的有效手段？课题以砷主要靶器官的正常细胞和癌细胞作为研究对象，分析砷作用后P53蛋白磷酸化水平及其下游因子的变化规律；同时构建WIP1低/高表达细胞模型以干预P53蛋白二阶段磷酸化的进程，检测细胞周期阻滞/DNA修复和凋亡，以阐明P53蛋白二阶段磷酸化修饰在低剂量砷暴露引起细胞增殖和治疗剂量砷处理诱导细胞凋亡中的关键作用，从而揭示砷"致癌与治癌"双重作用的分子机制。

Cell fate decision-proliferation or apoptosis-decides arsenic-exposure outcomes-carcinogenicity or chemotherapeutic effects. As the key cell fate decision maker, P53 governs cell survival/proliferation and apoptosis though a two-phase phosphorylation when responses to DNA damage, and WIP1, a dephosphorylation enzyme, is crucial in that P53 dynamical phosphorylation. Arsenic was reported to active P53 by DNA oxidative damage, suggesting that P53 may involved in arsenic-induced DNA damage response. Thus, we hypnotize that P53 may control cellular outcome by two-phase phosphorylation in arsenic-induced DNA damage response that leads to carcinogenicity or chemotherapeutic effects. To test this hypothesis, arsenic trioxide and sodium arsenite will be utilized, and tumor cells derived from arsenical target organs and their corresponding normal cells will be chosen as model cells. WIP1-specific siRNA/shRNA or plasmid DNA will be transfected to model cells to interfere the process of P53 two-phase phosphorylation. Then, the link between P53 phosphorylation levels and their following signal protein, and cellular outcome-cell cycle arrest and apoptosis will be examined to determine whether P53 two-phase phosphorylation is involved in low-level arsenic induced tumorigenesis and high-level arsenic induced chemotherapeutic effects. Our proposed research will significantly advance our understanding of the paradox of arsenic, and will further facilitate identification of WIP1 as a susceptive biomarker in arsenic carcinogenesis or new molecular target for improvement of arsenic treatment efficiency.