ATM orchestrates the DNA-damage response to counter toxic non-homologous end-joining at broken replication forks
ATM orchestrates the DNA-damage response to counter toxic non-homologous end-joining at broken replication forks
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DOI：
10.1038/s41467-018-07729-2
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发表时间：
2019-01-08
影响因子：
16.6
通讯作者：
Jacksom, Stephen P.
中科院分区：
文献类型：
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作者：
Balmus, Gabriel;Pilger, Domenic;Jacksom, Stephen P.
ATM肿瘤抑制基因的突变使其对DNA损伤的化疗药物具有超敏反应。为了探索遗传耐药机制，我们在DNA拓扑异构酶I抑制剂Topotecan处理的细胞中进行了全基因组CRISPR-Cas9筛选。因此，我们在这里建立了非同源末端连接(NHEJ)机制或BRCA1-A复合体的失活末端组件特异性地赋予ATM缺陷细胞拓扑替康抗性。我们发现ATM突变细胞对拓扑替康或多聚(ADP-核糖)聚合酶(PARP)抑制剂olaparib的超敏反应反映了同源重组在DNA复制分叉相关的单端双链断裂(DSB)上的延迟参与，使一些细胞受到毒性NHEJ的影响。NHEJ阻止DSB连接，或通过BRCA1-A复合体破坏促进同源重组，均可抑制这种毒性，突显ATM在防止有毒的LIG4介导的染色体融合中的关键作用。值得注意的是，ATM突变背景中的抑制子突变不同于BRCA1突变场景中的抑制突变，这表明患者分层的新机会和临床利用的额外治疗脆弱性。
Mutations in the ATM tumor suppressor gene confer hypersensitivity to DNA-damaging chemotherapeutic agents. To explore genetic resistance mechanisms, we performed genome-wide CRISPR-Cas9 screens in cells treated with the DNA topoisomerase I inhibitor topotecan. Thus, we here establish that inactivating terminal components of the non-homologous end-joining (NHEJ) machinery or of the BRCA1-A complex specifically confer topotecan resistance to ATM-deficient cells. We show that hypersensitivity of ATM-mutant cells to topotecan or the poly-(ADP-ribose) polymerase (PARP) inhibitor olaparib reflects delayed engagement of homologous recombination at DNA-replication-fork associated single-ended double-strand breaks (DSBs), allowing some to be subject to toxic NHEJ. Preventing DSB ligation by NHEJ, or enhancing homologous recombination by BRCA1-A complex disruption, suppresses this toxicity, highlighting a crucial role for ATM in preventing toxic LIG4-mediated chromosome fusions. Notably, suppressor mutations in ATM-mutant backgrounds are different to those in BRCA1-mutant scenarios, suggesting new opportunities for patient stratification and additional therapeutic vulnerabilities for clinical exploitation.