核仁蛋白FBL调控DNA损伤修复促进肿瘤发生发展的机制研究

DNA damage repair pathway plays a crucial role in maintaining genome stability. The functional deficiency or abundancy will disrupt the homeostasis of DNA repair pathway, which leads to tumorigenesis. Therefore, it is necessary to identify aberrant DNA damage molecules to facilitate early diagnosis and treatment for tumors. .In this project, we preliminarily discover the nucleolar marker FBL is involved in DNA damage repair pathway in tumor cells through screening from our established BioID-TBP-FOKI system. The higher expression of FBL exhibits in clinical colorectal cancer samples and colorectal cancer cells compared to normal cells and normal tissues. Mechanistically, we find that FBL directly regulates genomic DNA damage repair. It accumulates at the genomic DNA damage site under laser irradiation induced DNA damage in PARP1 dependent manner. Colorectal cancer is an inflammation-prone tumor, and its development is closely associated with abnormal DNA damage repair. Thus, we propose that the high expression of FBL would disrupt the homeostasis of DNA damage repair and promotes the development of colorectal cancer..Based on the previous works, the project is supposed to explore nucleolar protein FBL functions as a new component of DNA damage repair pathway besides nucleolar molecule in promoting tumorigenesis of colorectal cancer. This will give the new sight into exploring a new strategy for efficient and personal treatment for colorectal cancer in combining use of inhibitors targeting FBL-related DNA damage repair pathway.

正常的DNA损伤修复通路对维护机体基因组的稳定性至关重要，它的异常会破坏DNA修复稳态，诱发肿瘤的发生发展，因此鉴定DNA损伤异常分子对深入了解肿瘤的发生、协助肿瘤早期诊断和治疗至关重要。在此研究中，我们利用前期建立的基因组DNA损伤修复蛋白筛选方法 BioID-TBP-FOKI，发现了核仁蛋白FBL在肿瘤细胞中参与DNA损伤反应。在临床样本及肿瘤细胞中，我们鉴定到FBL在结直肠癌中有显著高表达。在机制研究上，我们发现FBL能直接参与基因组的DNA损伤修复，能在损伤后聚集到核质中的DNA损伤位点，并受DNA修复酶PARP1的调控。结直肠癌是炎症易发肿瘤，其肿瘤发生与DNA损伤修复异常密切相关。我们推测，FBL的高表达会破坏DNA损伤修复稳态，促进结直肠癌的发生发展。本项目拟在前期工作的基础上，以结直肠癌为模型，深入探讨核仁蛋白FBL参与基因组DNA损伤修复而促进结直肠癌发生发展的机制。

染色体不稳定(CIN)在结直肠癌的进展中起着核心作用。在这里，我们发现核仁蛋白FBL在结直肠癌组织中高表达，FBL的表达随着细胞内氧化应激水平的增加而升高，并可抵消掉氧化损伤，FBL的高表达能够有效地修复DNA损伤并减少DNA断裂。在机制上，我们发现FBL可以在PARP1调控下通过其N端的GAR结构域直接被招募到DNA损伤位点，被招募的FBL与PARP1相互作用而被PARP1进行聚腺苷二磷酸核糖基化并识别其他被修饰的蛋白。更重要的是，FBL主要通过招募Ku70/80复合物、并限制OGG1和FEN1的停留的方式来促进DNA双链末端连接修复，从而引起过度氧化损伤。FBL的高表达诱导染色体重排，并与结直肠癌中的CIN表型相关。因此，我们认为FBL是调节碱基切除修复(BER)转向末端连接修复的中心枢纽，这一过程也解释了癌症发生中为什么会有大量基因组重排。此外，我们的研究为PARP抑制剂应用于FBL高表达法的肿瘤病人从而对放疗增敏提供了一个潜在的前景。