CTCF is an essential epigenetic regulator mediating chromatin insulation, long-range regulatory interactions, and the organization of large topological domains in the nucleus. Phenotypes of CTCF haploinsufficient mutations in humans, knockout in mice, and depletion in cells are often consistent with impaired genome stability, but a role of CTCF in genome maintenance has not been fully investigated. Here, we report that CTCF maintains genome stability, is recruited to sites of DNA damage, and promotes homologous recombination repair of DNA double-strand breaks (DSBs). CTCF depletion increased chromosomal instability, marked by chromosome breakage and end fusions, elevated genotoxic stress-induced genomic DNA fragmentation, and activated the ataxia telangiectasia mutated (ATM) kinase. We show that CTCF could be recruited to drug-induced 53BP1 foci and known fragile sites, as well as to I-SceI endonuclease-induced DSBs. Laser irradiation analysis revealed that this recruitment depends on ATM, Nijmegen breakage syndrome (NBS), and the zinc finger DNA-binding domain of CTCF. We demonstrate that CTCF knockdown impaired homologous recombination (HR) repair of DSBs. Consistent with this, CTCF knockdown reduced the formation of γ-radiation–induced Rad51 foci, as well as the recruitment of Rad51 to laser-irradiated sites of DNA lesions and to I-SceI–induced DSBs. We further show that CTCF is associated with DNA HR repair factors MDC1 and AGO2, and directly interacts with Rad51 via its C terminus. These analyses establish a direct, functional role of CTCF in DNA repair and provide a potential link between genome organization and genome stability.

中文翻译：

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CTCF通过促进同源重组指导的DNA双链断裂修复来防止基因组不稳定

CTCF是必不可少的表观遗传调节剂，可介导染色质绝缘，长距离调节相互作用以及细胞核中大量拓扑结构域的组织。人中CTCF单倍型不足，小鼠基因敲除和细胞耗竭的表型通常与基因组稳定性受损相一致，但尚未全面研究CTCF在基因组维持中的作用。在这里，我们报道CTCF保持基因组稳定性，被募集到DNA损伤的位点，并促进DNA双链断裂（DSBs）的同源重组修复。CTCF耗竭增加了染色体的不稳定性，其特征是染色体断裂和末端融合，基因毒性应激诱导的基因组DNA片段升高，并激活了共济失调性毛细血管扩张突变（ATM）激酶。我们表明，CTCF可以募集到药物诱导的53BP1病灶和已知的易碎位点，以及I-SceI核酸内切酶诱导的DSBs。激光照射分析表明，这种募集取决于ATM，奈梅亨断裂综合征（NBS）和CTCF的锌指DNA结合域。我们证明，CTCF组合式受损损害DSBs的同源重组（HR）修复。与此相一致的是，CTCF敲低可减少γ辐射诱导的Rad51灶的形成，以及将Rad51募集到激光照射的DNA损伤部位和I-SceI诱导的DSB。我们进一步表明，CTCF与DNA HR修复因子MDC1和AGO2相关，并通过其C末端与Rad51直接相互作用。这些分析建立了直接的，