Department of Life Sciences, Chung-Ang University, Seoul 156-756, South Korea.
Department of Life Sciences, Chung-Ang University, Seoul 156-756, South Korea.
Mol Ther. 2018 Apr 4;26(4):1154-1165. doi: 10.1016/j.ymthe.2018.02.003. Epub 2018 Feb 8.
Homologous recombination (HR), which ensures accurate DNA replication and strand-break repair, is necessary to preserve embryonic stem cell (ESC) self-renewal. However, little is known about how HR factors modulate ESC differentiation and replication stress-associated DNA breaks caused by unique cell-cycle progression. Here, we report that ESCs utilize Rad51-dependent HR to enhance viability and induce rapid proliferation through a replication-coupled pathway. In addition, ESC differentiation was shown to be enhanced by ectopic expression of a subset of recombinases. Abundant expression of HR proteins throughout the ESC cycle, but not during differentiation, facilitated immediate HR-mediated repair of single-stranded DNA (ssDNA) gaps incurred during S-phase, via a mechanism that does not perturb cellular progression. Intriguingly, combined ectopic expression of two recombinases, Rad51 and Rad52, resulted in efficient ESC differentiation and diminished cell death, indicating that HR factors promote cellular differentiation by repairing global DNA breaks induced by chromatin remodeling signals. Collectively, these findings provide insight into the role of key HR factors in rapid DNA break repair following chromosome duplication during self-renewal and differentiation of ESCs.
同源重组（HR）可确保准确的 DNA 复制和链断裂修复，对于维持胚胎干细胞（ESC）的自我更新是必需的。然而，对于 HR 因子如何调节 ESC 分化以及由独特的细胞周期进程引起的与复制应激相关的 DNA 断裂，人们知之甚少。在这里，我们报告 ESC 利用 Rad51 依赖性 HR 通过复制偶联途径来增强活力并诱导快速增殖。此外，异位表达重组酶的亚组可增强 ESC 分化。HR 蛋白在整个 ESC 周期中的大量表达，但在分化过程中没有表达，这使得它们能够通过一种不会干扰细胞进程的机制，立即修复 S 期发生的单链 DNA（ssDNA）缺口的 HR 介导修复。有趣的是，两种重组酶 Rad51 和 Rad52 的异位共表达导致 ESC 分化效率提高且细胞死亡减少，表明 HR 因子通过修复染色质重塑信号诱导的全局 DNA 断裂来促进细胞分化。总的来说，这些发现为关键 HR 因子在 ESC 自我更新和分化过程中染色体复制后快速 DNA 断裂修复中的作用提供了新的见解。
