A universal feature of DNA damage and replication stress in eukaryotes is the activation of a checkpoint-kinase response. In S-phase, the checkpoint inhibits replication initiation, yet the function of this global block to origin firing remains unknown. To establish the physiological roles of this arm of the checkpoint, we analyzed separation of function mutants in the budding yeast Saccharomyces cerevisiae that allow global origin firing upon replication stress, despite an otherwise normal checkpoint response. Using genetic screens, we show that lack of the checkpoint-block to origin firing results in a dependence on pathways required for the resolution of topological problems. Failure to inhibit replication initiation indeed causes increased DNA catenation, resulting in DNA damage and chromosome loss. We further show that such topological stress is not only a consequence of a failed checkpoint response but also occurs in an unperturbed S-phase when too many origins fire simultaneously. Together we reveal that the role of limiting the number of replication initiation events is to prevent DNA topological problems, which may be relevant for the treatment of cancer with both topoisomerase and checkpoint inhibitors.

中文翻译：

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检查点抑制起源射击可防止 DNA 拓扑应力。

真核生物中 DNA 损伤和复制应激的一个普遍特征是检查点激酶反应的激活。在 S 阶段，检查点会抑制复制启动，但这个全局块对原始触发的功能仍然未知。为了确定检查点这一臂的生理作用，我们分析了发芽酵母酿酒酵母中功能突变体的分离，这些突变体允许在复制压力下启动全局起源，尽管检查点反应正常。使用遗传筛选，我们表明缺乏起源射击的检查点块会导致依赖于解决拓扑问题所需的路径。未能抑制复制启动确实会导致 DNA 连锁增加，从而导致 DNA 损伤和染色体丢失。我们进一步表明，这种拓扑应力不仅是检查点响应失败的结果，而且当太多起源同时触发时，也会发生在未受干扰的 S 阶段。我们共同揭示了限制复制起始事件数量的作用是防止 DNA 拓扑问题，这可能与拓扑异构酶和检查点抑制剂治疗癌症有关。