Morafraile Esther C, Diffley John F X, Tercero José Antonio, Segurado Mónica
Instituto de Biología Funcional y Genómica and Departamento de Microbiología y Genética, (CSIC/USAL), Campus Miguel de Unamuno, Salamanca 37007, Spain.
Cancer Research UK London Research Institute, Clare Hall Laboratories, South Mimms, Herts. EN6 3LD, United Kingdom.
Sci Rep. 2015 Jan 20;5:7886. doi: 10.1038/srep07886.
The checkpoint kinase Rad53 is crucial to regulate DNA replication in the presence of replicative stress. Under conditions that interfere with the progression of replication forks, Rad53 prevents Exo1-dependent fork degradation. However, although EXO1 deletion avoids fork degradation in rad53 mutants, it does not suppress their sensitivity to the ribonucleotide reductase (RNR) inhibitor hydroxyurea (HU). In this case, the inability to restart stalled forks is likely to account for the lethality of rad53 mutant cells after replication blocks. Here we show that Rad53 regulates replication restart through the checkpoint-dependent transcriptional response, and more specifically, through RNR induction. Thus, in addition to preventing fork degradation, Rad53 prevents cell death in the presence of HU by regulating RNR-expression and localization. When RNR is induced in the absence of Exo1 and RNR negative regulators, cell viability of rad53 mutants treated with HU is increased and the ability of replication forks to restart after replicative stress is restored.
关卡激酶Rad53对于在复制应激存在的情况下调节DNA复制至关重要。在干扰复制叉进展的条件下，Rad53可防止Exo1依赖性的叉降解。然而，尽管Exo1缺失可避免rad53突变体中的叉降解，但它并不能抑制其对核糖核苷酸还原酶（RNR）抑制剂羟基脲（HU）的敏感性。在这种情况下，无法重新启动停滞的叉可能是复制受阻后rad53突变体细胞致死的原因。我们在此表明，Rad53通过关卡依赖性转录反应，更具体地说，通过RNR诱导来调节复制重新启动。因此，除了防止叉降解外，Rad53还通过调节RNR的表达和定位来防止在HU存在时细胞死亡。当在没有Exo1和RNR负调节因子的情况下诱导RNR时，用HU处理的rad53突变体的细胞活力增加，并且复制叉在复制应激后重新启动的能力得以恢复。
