化疗是癌症治疗的重要手段，但化疗药物也会损伤正常细胞，引发一系列负面治疗结果。最近我们的研究发现酵母细胞在化疗药物羟基脲和雷帕霉素作用下表现出截然不同的演化模式，而且不同遗传背景的菌株对同种药物的应答速率明显不同。这些结果提示这两种药物对基因组稳定性及其演化具有不同的影响，且细胞自身的遗传背景也在这一过程中扮演重要角色。为了深入理解这两种化疗药物在不同遗传背景下对基因组稳定性的影响，本项目拟在前期研究基础上，利用4个遗传背景不同的酵母菌株在羟基脲和雷帕霉素环境下进行突变积累实验，通过至少1000代的中性演化在基因组上无差别地积累各种突变，结合二代和三代测序技术描绘基因组在药物作用下碱基水平和结构水平的突变图谱。该项目将帮助我们精确解析这两种化疗药物的诱变特征、机制及遗传背景相关性，从而帮助我们深入认识这两种药物对基因组稳定性的影响，为临床评估药物的基因组毒性和长期使用风险提供有价值的参考。

Chemotherapy is one of the most important approaches to treat cancer. However, the anti-cancer drugs are also harmful to normal cells, resulting in long-term side effects and even relapse. Recently, we found distinct evolutionary patterns of yeast cells when they were treated with hydroxyurea and rapamycin. Moreover, we found yeast strains with distinct genetic backgrounds responded to the drug in different rates. These results collectively suggest drug-specific and genetic-background-specific effects on the evolutionary trajectory of eukaryotic genomes. In order to comprehensively understand the effects of these drugs on genome stability as well as their interplays with different genetic backgrounds, we propose to apply mutation accumulation experiments to four yeast strains with distinct genetic backgrounds and propagate them in hydroxyurea and rapamycin. We will first propagate yeast cells for at least 1,000 generations through neutral evolution, which allows all kinds of mutations to accumulate in an unbiased way. Afterwards, we will use both next generation and third generation sequencing technologies to identify mutations at different scales, including both base-level mutations and large structural rearrangements. This experimental setup will not only enable us to delineate the mutagenesis patterns of hydroxyurea and rapamycin, but also allow us to dissect the interaction between drugs and genetic backgrounds. In sum, this project will illuminate the direct effects of chemotherapy on genome stability, leading to a better understanding of the long-term genotoxity of anti-cancer drugs in clinical treatments.