Wellcome Trust/Cancer Research United Kingdom Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom.
Elife. 2021 Jan 5;10:e63589. doi: 10.7554/eLife.63589.
Checkpoints maintain the order of cell cycle events during DNA damage or incomplete replication. How the checkpoint response is tailored to different phases of the cell cycle remains poorly understood. The S-phase checkpoint for example results in the slowing of replication, which in budding yeast occurs by Rad53-dependent inhibition of the initiation factors Sld3 and Dbf4. Despite this, we show here that Rad53 phosphorylates both of these substrates throughout the cell cycle at the same sites as in S-phase, suggesting roles for this pathway beyond S-phase. Indeed, we show that Rad53-dependent inhibition of Sld3 and Dbf4 limits re-replication in G2/M, preventing gene amplification. In addition, we show that inhibition of Sld3 and Dbf4 in G1 prevents premature initiation at all origins at the G1/S transition. This study redefines the scope of the 'S-phase checkpoint' with implications for understanding checkpoint function in cancers that lack cell cycle controls.
检查点在 DNA 损伤或不完全复制期间维持细胞周期事件的顺序。检查点反应如何针对细胞周期的不同阶段进行调整，目前仍知之甚少。例如，S 期检查点导致复制减速，在芽殖酵母中，这是通过 Rad53 依赖性抑制起始因子 Sld3 和 Dbf4 来实现的。尽管如此，我们在这里表明，Rad53 在整个细胞周期中都在与 S 期相同的位点上磷酸化这两种底物，表明该途径的作用超出了 S 期。事实上，我们表明，Rad53 依赖性抑制 Sld3 和 Dbf4 限制了 G2/M 中的再复制，防止了基因扩增。此外，我们还表明，在 G1 期抑制 Sld3 和 Dbf4 可防止在 G1/S 转换时所有起始点的过早起始。这项研究重新定义了“S 期检查点”的范围，对理解缺乏细胞周期控制的癌症中的检查点功能具有重要意义。
