Safeguarding replication fork stability in transcriptionally active regions is crucial for precise DNA replication and mutation prevention. Here, we discover the pervasive existence of replication fork-associated RNA-DNA hybrids (RF-RDs) in transcriptionally active regions of human cells. These hybrids function as protective barriers, preventing DNA2-mediated nascent DNA degradation and replication fork collapse under replication stress. We also identify DDX39A as a RAD51-associated protein that binds to stalled forks and resolves RF-RDs, facilitating proper DNA2-mediated DNA resection and replication fork restart. Excessive dissolution of RF-RDs causes replication fork collapse and genomic instability, while insufficient dissolution of RF-RDs under replication stress increases fork stability, resulting in chemoresistance that can be reversed by eliminating RF-RDs. In summary, we elucidated the prevalence of RF-RDs at replication forks within transcriptionally active regions, revealed their pivotal role in safeguarding replication fork stability, and proposed that targeting RF-RDs holds promise for augmenting chemotherapeutic efficacy.

中文翻译：

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DDX39A 解析复制叉相关的 RNA-DNA 杂交体，以平衡叉保护和切割，以维持基因组稳定性


保护转录活性区域的复制叉稳定性对于精确的 DNA 复制和突变预防至关重要。在这里，我们发现在人类细胞的转录活性区域普遍存在复制叉相关的 RNA-DNA 杂交体 （RF-RDs）。这些杂交体起到保护屏障的作用，防止 DNA2 介导的新生 DNA 降解和复制叉在复制应激下崩溃。我们还将 DDX39A 鉴定为 RAD51 相关蛋白，它与停滞的分叉结合并解析 RF-RD，促进 DNA2 介导的正确 DNA 切除和复制叉重启。RF-RDs 的过度溶解会导致复制叉崩溃和基因组不稳定，而 RF-RDs 在复制应力下的溶解不足会增加叉的稳定性，从而导致化疗耐药性，可以通过消除 RF-RDs 来逆转。总之，我们阐明了 RF-RDs 在转录活性区域内复制叉中的普遍性，揭示了它们在保护复制叉稳定性方面的关键作用，并提出靶向 RF-RDs 有望提高化疗疗效。