Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
Cancer Research Center of Marseille, CNRS UMR7258, Inserm U1068, Institut Paoli-Calmettes, Aix-Marseille Université U105, Marseille, France.
Cell Rep. 2018 Jul 17;24(3):538-545. doi: 10.1016/j.celrep.2018.06.061.
RAD51 promotes homologous recombination repair (HR) of double-strand breaks and acts during DNA replication to facilitate fork reversal and protect nascent DNA strands from nuclease digestion. Several additional HR proteins regulate fork protection by promoting RAD51 filament formation. Here, we show that RADX modulates stalled fork protection by antagonizing RAD51. Consequently, silencing RADX restores fork protection in cells deficient for BRCA1, BRCA2, FANCA, FANCD2, or BOD1L. Inactivating RADX prevents both MRE11- and DNA2-dependent fork degradation. Furthermore, RADX overexpression causes fork degradation that is dependent on these nucleases and fork reversal. The amount of RAD51 determines the fate of stalled replication forks, with more RAD51 required for fork protection than fork reversal. Finally, we find that RADX effectively competes with RAD51 for binding to single-stranded DNA, supporting a model in which RADX buffers RAD51 to ensure the right amount of reversal and protection to maintain genome stability.
RAD51 促进双链断裂的同源重组修复 (HR)，并在 DNA 复制过程中发挥作用，以促进叉的反转并保护新生 DNA 链免受核酸酶的消化。其他几种 HR 蛋白通过促进 RAD51 丝形成来调节叉的保护。在这里，我们表明 RADX 通过拮抗 RAD51 来调节停滞的叉保护。因此，沉默 RADX 可恢复 BRCA1、BRCA2、FANCA、FANCD2 或 BOD1L 缺陷细胞中的叉保护。RADX 的失活可防止 MRE11 和 DNA2 依赖性叉降解。此外，RADX 过表达导致依赖于这些核酸酶和叉反转的叉降解。RAD51 的数量决定了停滞复制叉的命运，保护叉所需的 RAD51 比反转叉更多。最后，我们发现 RADX 可有效地与 RAD51 竞争结合单链 DNA，支持 RADX 缓冲 RAD51 以确保正确的反转和保护量以维持基因组稳定性的模型。
