Forey Romain, Poveda Ana, Sharma Sushma, Barthe Antoine, Padioleau Ismael, Renard Claire, Lambert Robin, Skrzypczak Magdalena, Ginalski Krzysztof, Lengronne Armelle, Chabes Andrei, Pardo Benjamin, Pasero Philippe
Institut de Génétique Humaine, CNRS, Université de Montpellier, Montpellier, France.
Institut de Génétique Humaine, CNRS, Université de Montpellier, Montpellier, France; Instituto de Investigación en Salud Pública y Zoonosis, Facultad de Ciencias Químicas, Universidad Central del Ecuador, Quito, Ecuador.
Mol Cell. 2020 May 7;78(3):396-410.e4. doi: 10.1016/j.molcel.2020.02.021. Epub 2020 Mar 12.
The Mec1 and Rad53 kinases play a central role during acute replication stress in budding yeast. They are also essential for viability in normal growth conditions, but the signal that activates the Mec1-Rad53 pathway in the absence of exogenous insults is currently unknown. Here, we show that this pathway is active at the onset of normal S phase because deoxyribonucleotide triphosphate (dNTP) levels present in G phase may not be sufficient to support processive DNA synthesis and impede DNA replication. This activation can be suppressed experimentally by increasing dNTP levels in G phase. Moreover, we show that unchallenged cells entering S phase in the absence of Rad53 undergo irreversible fork collapse and mitotic catastrophe. Together, these data indicate that cells use suboptimal dNTP pools to detect the onset of DNA replication and activate the Mec1-Rad53 pathway, which in turn maintains functional forks and triggers dNTP synthesis, allowing the completion of DNA replication.
Mec1和Rad53激酶在芽殖酵母的急性复制应激过程中发挥核心作用。它们对于正常生长条件下的生存能力也是必不可少的，但是在没有外源性损伤的情况下激活Mec1-Rad53途径的信号目前尚不清楚。在这里，我们表明该途径在正常S期开始时就处于活跃状态，因为G期存在的脱氧核糖核苷酸三磷酸（dNTP）水平可能不足以支持连续的DNA合成并阻碍DNA复制。通过在G期增加dNTP水平，可以通过实验抑制这种激活。此外，我们表明，在没有Rad53的情况下进入S期的未受挑战的细胞会经历不可逆的叉状塌陷和有丝分裂灾难。总之，这些数据表明，细胞利用次优的dNTP库来检测DNA复制的开始并激活Mec1-Rad53途径，这反过来又维持功能性叉状结构并触发dNTP合成，从而使DNA复制得以完成。
