Institute of Molecular Cancer Research, University of Zurich, CH-8057 Zurich, Switzerland and Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 14300 Prague, Czech Republic.
Nucleic Acids Res. 2014 Feb;42(4):2380-90. doi: 10.1093/nar/gkt1263. Epub 2013 Dec 6.
Most mitotic homologous recombination (HR) events proceed via a synthesis-dependent strand annealing mechanism to avoid crossing over, which may give rise to chromosomal rearrangements and loss of heterozygosity. The molecular mechanisms controlling HR sub-pathway choice are poorly understood. Here, we show that human RECQ5, a DNA helicase that can disrupt RAD51 nucleoprotein filaments, promotes formation of non-crossover products during DNA double-strand break-induced HR and counteracts the inhibitory effect of RAD51 on RAD52-mediated DNA annealing in vitro and in vivo. Moreover, we demonstrate that RECQ5 deficiency is associated with an increased occupancy of RAD51 at a double-strand break site, and it also causes an elevation of sister chromatid exchanges on inactivation of the Holliday junction dissolution pathway or on induction of a high load of DNA damage in the cell. Collectively, our findings suggest that RECQ5 acts during the post-synaptic phase of synthesis-dependent strand annealing to prevent formation of aberrant RAD51 filaments on the extended invading strand, thus limiting its channeling into potentially hazardous crossover pathway of HR.
大多数有丝分裂同源重组（HR）事件通过依赖合成的链退火机制进行，以避免交叉，这可能导致染色体重排和杂合性丢失。控制 HR 亚途径选择的分子机制知之甚少。在这里，我们表明，人 RECQ5 是一种可以破坏 RAD51 核蛋白丝的 DNA 解旋酶，它在 DNA 双链断裂诱导的 HR 过程中促进非交叉产物的形成，并抵消 RAD51 对 RAD52 介导的 DNA 退火的抑制作用，无论是在体外还是体内。此外，我们证明 RECQ5 缺陷与 RAD51 在双链断裂位点的占有率增加有关，它还导致在霍利迪连接解旋途径失活或在细胞中诱导高负荷 DNA 损伤时姐妹染色单体交换的增加。总的来说，我们的研究结果表明，RECQ5 在依赖合成的链退火的后突触阶段发挥作用，以防止在延伸的入侵链上形成异常的 RAD51 丝，从而限制其进入 HR 的潜在危险交叉途径。
