James Ryan C, Wang Jerry K, Bhatt Siddhanth R, Shadid Sophie E, Phuong Daryl J, Schimenti John C
Cornell University, Dept. of Biomedical Sciences, Ithaca, NY 14853, USA.
Cornell University, Dept. of Molecular Biology & Genetics, Ithaca, NY, 14853, USA.
bioRxiv. 2025 May 18:2025.05.16.654332. doi: 10.1101/2025.05.16.654332.
Genome maintenance is of the utmost importance in stem cells, as mutations can be propagated and cause defects in derivative tissues. Many stem cell types display low mutation rates, with embryonic stem cells (ESCs) being a notable example. The bases for this property are unclear but may be achieved by optimization of various processes including high-fidelity DNA repair, cell cycle checkpoint controls, and hypersensitivity to genotoxic insults that trigger cell death. Here, we investigate the mechanisms underlying the unique responses of mouse ESCs (mESCs) to replication stress (RS) using an array of small molecule inhibitors and genotoxins. We find that whereas mESCs survive under acute RS in an ATR- and CHK1-dependent manner similar to somatic cells, they lack a strong G2/M checkpoint and fail to repair DNA crosslinks in the absence of ATR signaling. Despite the lack of a strong G2/M checkpoint, mESCs maintain a spindle assembly checkpoint (SAC). We posit that mESCs preferentially repair DNA crosslinks in S phase via homology-directed mechanisms, and cells that fail to complete repair before mitosis undergo mitotic catastrophe and cell death. These findings shed light on mutation avoidance mechanisms in ESCs that may extend to other stem cell types.
基因组维持在干细胞中至关重要，因为突变可能会传播并导致衍生组织出现缺陷。许多干细胞类型的突变率较低，胚胎干细胞（ESC）就是一个显著的例子。这种特性的基础尚不清楚，但可能是通过优化各种过程来实现的，包括高保真DNA修复、细胞周期检查点控制以及对引发细胞死亡的基因毒性损伤的超敏反应。在这里，我们使用一系列小分子抑制剂和基因毒素来研究小鼠胚胎干细胞（mESC）对复制应激（RS）的独特反应背后的机制。我们发现，虽然mESC在急性RS下以类似于体细胞的依赖ATR和CHK1的方式存活，但它们缺乏强大的G2/M检查点，并且在没有ATR信号的情况下无法修复DNA交联。尽管缺乏强大的G2/M检查点，但mESC维持着纺锤体组装检查点（SAC）。我们推测，mESC在S期通过同源定向机制优先修复DNA交联，而在有丝分裂前未能完成修复的细胞会经历有丝分裂灾难和细胞死亡。这些发现揭示了ESC中可能扩展到其他干细胞类型的避免突变机制。
