TP53功能缺陷导致的氧化压力对基因组不稳定性的促进作用及机制研究

TP53 is the most commonly mutated or deleted tumor suppressor gene in cancer. One of the consequences of TP53 dysfunction is increased genomic instability. While it is known that p53, encoded by TP53, regulates multiple biological processes, including cell cycle checkpoint, apoptosis, senescence and redox regulation, it is unclear how each of the p53-regulated pathways contributes to the maintenance of genomic stability. We hypothesize that the antioxidant function of p53 is most important for genomic integrity. We propose to first characterize the genomic changes in normal human fibroblasts under oxidative stress, by analyzing the somatic mutations at HPRT locus and the genome-wide copy number changes (CNC) and loss of heterozygosity (LOH). We will then analyze HPRT mutations and genome-wide CNC/LOH in TP53-deficient human fibroblasts and compare them with those induced by oxidative stress. The roles of representative p53 target genes known to have antioxidant function will also be tested. This study will advance our understanding of the tumor-suppressive function of p53 and how p53 dysfunction contributes to genomic instability.

抑癌基因TP53在多数肿瘤中发生突变或缺失，其后果之一是导致基因组不稳定性升高。基因组不稳定性既是肿瘤发生的起始因素，又是肿瘤发展的促进因素。TP53产物p53通过转录激活一系列靶基因参与众多生物学过程的调控，包括细胞周期、DNA修复、细胞凋亡、细胞衰老、糖代谢、活性氧（ROS）稳态平衡等， 但在众多p53调控的通路中是哪些通路在基因组稳定性维持方面发挥更大的作用尚不明确。本课题将验证以下假说：生理状态下p53维持基因组稳定性的功能主要是通过其抗氧化作用实现的。本研究将通过分析HPRT报告基因突变和全基因组DNA拷贝数变化情况，解析氧化损伤导致人类成纤维细胞基因组改变的规律和特征；研究p53缺陷导致正常人类成纤维细胞基因组不稳定性的特征，明晰p53缺陷情况下的基因组改变是否呈现氧化压力诱导的特征；明确代表性p53靶基因在抗氧化及维持基因组稳定性中的作用。

抑癌基因TP53 产物 p53 通过转录激活一系列靶基因调控众多生物学过程，包括细胞周期、细胞衰老、活性氧（ROS）的稳态维持等。本课题主要就p53如何通过调控氧自由基水平影响基因组稳定性和细胞衰老开展了研究。通过研究进一步确定了氧自由基在在诱发DNA损伤和驱动基因组稳定性中的作用。发现p53靶基因RRAD虽然在衰老细胞中上调，RRAD却具有抗氧化功能，因而发挥抗衰老的作用。发现了p53-MDM2通过下调DYRK1A-EGFR通路驱动细胞衰老的新机制，证明了MDM2通过泛素化降解DYRK1A下调EGFR及其下游的ERK信号通路。揭示了细胞周期阻滞通过线粒体堆积升高超氧阴离子进而驱动基因组不稳定性的新机制。这些结果对认识p53在细胞生存和基因组稳定性中的功能提供了新的视角。