Galli Michela, Frigerio Chiara, Colombo Chiara Vittoria, Casari Erika, Longhese Maria Pia, Clerici Michela
Dipartimento di Biotecnologie e Bioscienze, Università degli Studi di Milano-Bicocca, Milano, Italy.
iScience. 2024 Jun 28;27(8):110410. doi: 10.1016/j.isci.2024.110410. eCollection 2024 Aug 16.
Tel1/ataxia telangiectasia mutated (ATM) kinase plays multiple functions in response to DNA damage, promoting checkpoint-mediated cell-cycle arrest and repair of broken DNA. In addition, Tel1 stabilizes replication forks that arrest upon the treatment with the topoisomerase poison camptothecin (CPT). We discover that inactivation of the Exo1 nuclease exacerbates the sensitivity of Tel1-deficient cells to CPT and other agents that hamper DNA replication. Furthermore, cells lacking both Exo1 and Tel1 activities exhibit sustained checkpoint activation in the presence of CPT, indicating that Tel1 and Exo1 limit the activation of a Mec1-dependent checkpoint. The absence of Tel1 or its kinase activity enhances recombination between inverted DNA repeats induced by replication fork blockage in an Exo1-dependent manner. Thus, we propose that Exo1 processes intermediates arising at stalled forks in mutants to promote DNA replication recovery and cell survival.
Tel1/毛细血管扩张性共济失调突变（ATM）激酶在应对DNA损伤时发挥多种功能，促进检查点介导的细胞周期停滞以及断裂DNA的修复。此外，Tel1可稳定因拓扑异构酶毒药喜树碱（CPT）处理而停滞的复制叉。我们发现，Exo1核酸酶失活会加剧Tel1缺陷细胞对CPT和其他阻碍DNA复制的试剂的敏感性。此外，缺乏Exo1和Tel1活性的细胞在存在CPT的情况下表现出持续的检查点激活，表明Tel1和Exo1限制了Mec1依赖性检查点的激活。Tel1缺失或其激酶活性的缺失会以Exo1依赖性方式增强由复制叉阻滞诱导的反向DNA重复序列之间的重组。因此，我们提出Exo1处理突变体中停滞叉处产生的中间体，以促进DNA复制恢复和细胞存活。
