Institut Curie, Université PSL, CNRS UMR3348, Orsay, France.
Université Paris-Saclay, CNRS UMR3348, Orsay, France.
EMBO J. 2021 Apr 1;40(7):e106018. doi: 10.15252/embj.2020106018. Epub 2021 Feb 26.
The BRCA2 tumor suppressor is a DNA double-strand break (DSB) repair factor essential for maintaining genome integrity. BRCA2-deficient cells spontaneously accumulate DNA-RNA hybrids, a known source of genome instability. However, the specific role of BRCA2 on these structures remains poorly understood. Here we identified the DEAD-box RNA helicase DDX5 as a BRCA2-interacting protein. DDX5 associates with DNA-RNA hybrids that form in the vicinity of DSBs, and this association is enhanced by BRCA2. Notably, BRCA2 stimulates the DNA-RNA hybrid-unwinding activity of DDX5 helicase. An impaired BRCA2-DDX5 interaction, as observed in cells expressing the breast cancer variant BRCA2-T207A, reduces the association of DDX5 with DNA-RNA hybrids, decreases the number of RPA foci, and alters the kinetics of appearance of RAD51 foci upon irradiation. Our findings are consistent with DNA-RNA hybrids constituting an impediment for the repair of DSBs by homologous recombination and reveal BRCA2 and DDX5 as active players in their removal.
BRCA2 肿瘤抑制因子是一种 DNA 双链断裂 (DSB) 修复因子，对维持基因组完整性至关重要。BRCA2 缺陷细胞会自发积累 DNA-RNA 杂交物，这是已知的基因组不稳定的来源。然而，BRCA2 对这些结构的具体作用仍知之甚少。在这里，我们鉴定出 DEAD 盒 RNA 解旋酶 DDX5 是 BRCA2 的相互作用蛋白。DDX5 与在 DSB 附近形成的 DNA-RNA 杂交物结合，BRCA2 增强了这种结合。值得注意的是，BRCA2 刺激 DDX5 解旋酶的 DNA-RNA 杂交物解旋活性。在表达乳腺癌变体 BRCA2-T207A 的细胞中观察到的 BRCA2-DDX5 相互作用受损，会降低 DDX5 与 DNA-RNA 杂交物的结合，减少 RPA 焦点的数量，并改变照射后 RAD51 焦点出现的动力学。我们的研究结果表明，DNA-RNA 杂交物构成了同源重组修复 DSB 的障碍，并揭示了 BRCA2 和 DDX5 是其去除的有效参与者。
