Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California, USA; School of Medicine, Nankai University, Tianjin, China.
Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California, USA.
J Biol Chem. 2023 Jan;299(1):102770. doi: 10.1016/j.jbc.2022.102770. Epub 2022 Dec 5.
G-quadruplex (G4)-forming DNA sequences are abundant in the human genome, and they are hot spots for inducing DNA double-strand breaks (DSBs) and genome instability. The mechanisms involved in protecting G4s and maintaining genome stability have not been fully elucidated. Here, we demonstrated that RAD52 plays an important role in suppressing DSB accumulation at G4s, and RAD52-deficient cells are sensitive to G4-stabilizing compounds. Mechanistically, we showed that RAD52 is required for efficient homologous recombination repair at G4s, likely due to its function in recruiting structure-specific endonuclease XPF to remove G4 structures at DSB ends. We also demonstrated that upon G4 stabilization, endonuclease MUS81 mediates cleavage of stalled replication forks at G4s. The resulting DSBs recruit RAD52 and XPF to G4s for processing DSB ends to facilitate homologous recombination repair. Loss of RAD52 along with G4-resolving helicase FANCJ leads to a significant increase of DSB accumulation before and after treatment with the G4-stabilizing compound pyridostatin, and RAD52 exhibits a synthetic lethal interaction with FANCJ. Collectively, our findings reveal a new role of RAD52 in protecting G4 integrity and provide insights for new cancer treatment strategies.
G-四链体（G4）形成的 DNA 序列在人类基因组中大量存在，它们是诱导 DNA 双链断裂（DSB）和基因组不稳定的热点。保护 G4 并维持基因组稳定性的机制尚未完全阐明。在这里，我们证明 RAD52 在抑制 G4 处 DSB 积累中发挥重要作用，RAD52 缺陷细胞对 G4 稳定化合物敏感。从机制上讲，我们表明 RAD52 是 G4 处同源重组修复的有效所需的，可能是由于其功能在于招募结构特异性内切酶 XPF 以去除 DSB 末端的 G4 结构。我们还证明，在 G4 稳定后，核酸内切酶 MUS81 介导 G4 处停滞复制叉的切割。由此产生的 DSB 招募 RAD52 和 XPF 到 G4 以处理 DSB 末端，以促进同源重组修复。在用 G4 稳定化合物吡啶酮处理前后，RAD52 的缺失以及 G4 解旋酶 FANCJ 的缺失导致 DSB 积累显著增加，并且 RAD52 与 FANCJ 表现出合成致死相互作用。总之，我们的研究结果揭示了 RAD52 在保护 G4 完整性中的新作用，并为新的癌症治疗策略提供了见解。
