DNA Damage Response Laboratory, Cancer Research UK, Clare Hall Laboratories, South Mimms EN6 3LD, UK.
Mol Cell. 2010 Jan 29;37(2):259-72. doi: 10.1016/j.molcel.2009.12.026.
Homologous recombination (HR) is essential for repair of meiotic DNA double-strand breaks (DSBs). Although the mechanisms of RAD-51-DNA filament assembly and strand exchange are well characterized, the subsequent steps of HR are less well defined. Here, we describe a synthetic lethal interaction between the C. elegans helicase helq-1 and RAD-51 paralog rfs-1, which results in a block to meiotic DSB repair after strand invasion. Whereas RAD-51-ssDNA filaments assemble at meiotic DSBs with normal kinetics in helq-1, rfs-1 double mutants, persistence of RAD-51 foci and genetic interactions with rtel-1 suggest a failure to disassemble RAD-51 from strand invasion intermediates. Indeed, purified HELQ-1 and RFS-1 independently bind to and promote the disassembly of RAD-51 from double-stranded, but not single-stranded, DNA filaments via distinct mechanisms in vitro. These results indicate that two compensating activities are required to promote postsynaptic RAD-51 filament disassembly, which are collectively essential for completion of meiotic DSB repair.
同源重组(HR)对于修复减数分裂 DNA 双链断裂(DSBs)至关重要。尽管 RAD-51-DNA 丝组装和链交换的机制已经得到很好的描述,但 HR 的后续步骤定义得较少。在这里,我们描述了秀丽隐杆线虫解旋酶 helq-1 和 RAD-51 同源物 rfs-1 之间的合成致死相互作用,这导致在链入侵后减数分裂 DSB 修复受阻。虽然在 helq-1;rfs-1 双突变体中,RAD-51-ssDNA 丝以正常动力学组装在减数分裂 DSB 上,但 RAD-51 焦点的持续存在和与 rtel-1 的遗传相互作用表明,从链入侵中间体中无法解聚 RAD-51。事实上,体外纯化的 HELQ-1 和 RFS-1 独立地结合并通过不同的机制促进 RAD-51 从双链而非单链 DNA 丝上的解聚。这些结果表明,需要两种补偿活性来促进突触后 RAD-51 丝的解聚,这对于完成减数分裂 DSB 修复是必不可少的。
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