Accumulation of DNA–RNA hybrids in the form of R-loops can result in replication–transcription conflict that leads to the formation of DNA double strand breaks (DSBs). Using null mutants for the two Caenorhabditis elegans genes encoding for RNaseH1 and RNaseH2, we identify novel effects of R-loop accumulation in the germline. R-loop accumulation leads, as expected, to replication stress, followed by the formation of DSBs. A subset of these DSBs are irreparable. However, unlike irreparable DSBs generated in other systems, which trigger permanent cell cycle arrest, germline irreparable DSBs are propagated to oocytes. Despite DNA damage checkpoint activation in the stem cell niche, the signaling cannot be sustained and nuclei with irreparable DNA damage progress into meiosis. Moreover, unlike other forms of DNA damage that increase germline apoptosis, R-loop-generated DSBs remain undetected by the apoptotic checkpoint. This coincides with attenuation of ATM/ATR signaling in mid-to-late meiotic prophase I. These data altogether indicate that in the germline, DSBs that are generated by R-loops can lead to irreparable DSBs that evade cellular machineries designed for damage recognition. These studies implicate germline R-loops as an especially dangerous driver of germline mutagenesis.

中文翻译：

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R-loop 诱导的不可修复的 DNA 损伤逃避了 C. elegans 种系中的检查点检测

以 R 环形式积累的 DNA-RNA 杂合体可导致复制-转录冲突，从而导致 DNA 双链断裂 (DSB) 的形成。使用编码 RNaseH1 和 RNaseH2 的两个秀丽隐杆线虫基因的无效突变体，我们确定了生殖系中 R 环积累的新作用。正如预期的那样，R 环积累导致复制压力，然后形成 DSB。这些 DSB 的一个子集是不可修复的。然而，与其他系统中产生的触发永久细胞周期停滞的不可修复的 DSB 不同，种系不可修复的 DSB 会传播到卵母细胞。尽管干细胞生态位中的 DNA 损伤检查点激活，但信号传导无法持续，具有不可修复的 DNA 损伤的细胞核进入减数分裂。此外，与增加生殖细胞凋亡的其他形式的 DNA 损伤不同，R 环生成的 DSB 仍未被凋亡检查点检测到。这与减数分裂前期 I 中晚期 ATM/ATR 信号的衰减相吻合。这些数据完全表明，在生殖系中，由 R 环产生的 DSB 可导致无法修复的 DSB，从而逃避为损伤识别而设计的细胞机器。这些研究表明生殖系 R 环是生殖系诱变的一个特别危险的驱动因素。