Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, and Chinese Academy of Medical Sciences Research Unit, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, and Chinese Academy of Medical Sciences Research Unit, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Exp Cell Res. 2020 Nov 1;396(1):112242. doi: 10.1016/j.yexcr.2020.112242. Epub 2020 Aug 28.
FAM122A is a housekeeping gene and highly conserved in mammals. More recently, we have demonstrated that FAM122A is essential for maintaining the growth of hepatocellular carcinoma cells, in which we unexpectedly found that FAM122A deletion increases γH2AX protein level, suggesting that FAM122A may participate in the regulation of DNA homeostasis or stability. In this study, we continued to investigate the potential role of FAM122A in DNA damage and/or repair. We found that CRISPR/Cas9-mediated FAM122A deletion enhances endogenous DNA damages in cancer cells but not in normal cells, demonstrating a significant increase in γH2AX protein and foci formation of γH2AX and 53BP1, as well as DNA breaks by comet assay. Further, we found that FAM122A deletion greatly increases TOP2α protein level, and significantly and specifically enhances TOP2 poisons (etoposide and doxorubicin)-induced DNA damage effects in cancer cells. Moreover, FAM122A is found to be interacted with TOP2α, instead of TOP2β. However, FAM122A knockout doesn't affect the intracellular ROS levels and the process of DNA repair after removal of etoposide with short-term stimulation, suggesting that FAM122A deletion-enhanced DNA damage does not result from endogenous overproduction of ROS and/or impairment of DNA repair ability. Collectively, our study provides the first demonstration that FAM122A is critical for maintaining DNA stability probably by modulating TOP2α protein, and FAM122A deletion combined with TOP2-targeted drugs may represent a potential novel chemotherapeutic strategy for cancer patients.
FAM122A 是管家基因，在哺乳动物中高度保守。最近，我们已经证明 FAM122A 对于维持肝癌细胞的生长是必不可少的，在这过程中，我们出乎意料地发现 FAM122A 的缺失会增加 γH2AX 蛋白水平，这表明 FAM122A 可能参与调节 DNA 稳态或稳定性。在这项研究中，我们继续研究 FAM122A 在 DNA 损伤和/或修复中的潜在作用。我们发现 CRISPR/Cas9 介导的 FAM122A 缺失增强了癌细胞中的内源性 DNA 损伤，但在正常细胞中没有，这表明 γH2AX 蛋白和 γH2AX 和 53BP1 的焦点形成以及彗星试验中的 DNA 断裂显著增加。此外，我们发现 FAM122A 缺失大大增加了 TOP2α 蛋白水平，并显著且特异性地增强了 TOP2 抑制剂（依托泊苷和阿霉素）在癌细胞中诱导的 DNA 损伤效应。此外，发现 FAM122A 与 TOP2α 相互作用，而不是 TOP2β。然而，FAM122A 敲除并不影响细胞内 ROS 水平以及短时间依托泊苷刺激后 DNA 修复过程，这表明 FAM122A 缺失增强的 DNA 损伤不是由于内源性 ROS 过度产生和/或 DNA 修复能力受损所致。总之，我们的研究首次表明 FAM122A 对于维持 DNA 稳定性至关重要，可能是通过调节 TOP2α 蛋白，而 FAM122A 缺失与 TOP2 靶向药物联合使用可能为癌症患者代表一种潜在的新化疗策略。
