Replication protein A (RPA) is a major regulator of eukaryotic DNA metabolism involved in multiple essential cellular processes. Maintaining appropriate RPA dynamics is crucial for cells to prevent RPA exhaustion, which can lead to replication fork breakage and replication catastrophe. However, how cells regulate RPA availability during unperturbed replication and in response to stress has not been well elucidated. Here, we show that HNRNPA2B1^SUMO functions as an endogenous inhibitor of RPA during normal replication. HNRNPA2B1^SUMO associates with RPA through recognizing the SUMO-interacting motif (SIM) of RPA to inhibit RPA accumulation at replication forks and impede local ATR activation. Declining HNRNPA2^SUMO induced by DNA damage will release nuclear soluble RPA to localize to chromatin and enable ATR activation. Furthermore, we characterize that HNRNPA2B1 hinders homologous recombination (HR) repair via limiting RPA availability, thus conferring sensitivity to PARP inhibitors. These findings establish HNRNPA2B1 as a critical player in RPA-dependent surveillance networks.

复制蛋白 A (RPA) 是参与多种重要细胞过程的真核 DNA 代谢的主要调节因子。维持适当的 RPA 动态对于细胞防止 RPA 耗尽至关重要，否则可能导致复制叉断裂和复制灾难。然而，细胞在不受干扰的复制过程中以及响应压力时如何调节 RPA 的可用性尚未得到很好的阐明。在这里，我们证明 HNRNPA2B1 ^SUMO在正常复制过程中充当 RPA 的内源抑制剂。 HNRNPA2B1 ^SUMO通过识别 RPA 的 SUMO 相互作用基序 (SIM) 与 RPA 结合，抑制 RPA 在复制叉处的积累并阻碍局部 ATR 激活。 DNA 损伤诱导的 HNRNPA2 ^SUMO下降将释放核可溶性 RPA，定位于染色质并激活 ATR。此外，我们还发现 HNRNPA2B1 通过限制 RPA 的可用性来阻碍同源重组 (HR) 修复，从而赋予对 PARP 抑制剂的敏感性。这些发现表明 HNRNPA2B1 是依赖 RPA 的监控网络中的关键参与者。