DNA-protein crosslinks (DPCs) obstruct essential DNA transactions, posing a serious threat to genome stability and functionality. DPCs are proteolytically processed in a ubiquitin- and DNA replication-dependent manner by SPRTN and the proteasome but can also be resolved via targeted SUMOylation. However, the mechanistic basis of SUMO-mediated DPC resolution and its interplay with replication-coupled DPC repair remain unclear. Here, we show that the SUMO-targeted ubiquitin ligase RNF4 defines a major pathway for ubiquitylation and proteasomal clearance of SUMOylated DPCs in the absence of DNA replication. Importantly, SUMO modifications of DPCs neither stimulate nor inhibit their rapid DNA replication-coupled proteolysis. Instead, DPC SUMOylation provides a critical salvage mechanism to remove DPCs formed after DNA replication, as DPCs on duplex DNA do not activate interphase DNA damage checkpoints. Consequently, in the absence of the SUMO-RNF4 pathway cells are able to enter mitosis with a high load of unresolved DPCs, leading to defective chromosome segregation and cell death. Collectively, these findings provide mechanistic insights into SUMO-driven pathways underlying replication-independent DPC resolution and highlight their critical importance in maintaining chromosome stability and cellular fitness.

中文翻译：

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SUMO-RNF4通路不依赖DNA复制的DNA-蛋白质交联修复的机制和功能

DNA-蛋白质交联 (DPC) 阻碍了基本的 DNA 交易，对基因组的稳定性和功能构成严重威胁。SPRTN 和蛋白酶体以泛素和 DNA 复制依赖性方式对 DPC 进行蛋白水解处理，但也可以通过靶向 SUMO 化来解决。然而，SUMO 介导的 DPC 分辨率的机制基础及其与复制耦合 DPC 修复的相互作用仍不清楚。在这里，我们表明 SUMO 靶向泛素连接酶 RNF4 定义了在没有 DNA 复制的情况下 SUMO 化 DPC 泛素化和蛋白酶体清除的主要途径。重要的是，DPC 的 SUMO 修饰既不刺激也不抑制其快速的 DNA 复制偶联蛋白水解。相反，DPC SUMOylation 提供了一种关键的补救机制来去除 DNA 复制后形成的 DPC，因为双链 DNA 上的 DPC 不会激活间期 DNA 损伤检查点。因此，在没有 SUMO-RNF4 途径的情况下，细胞能够以高负荷的未解析 DPC 进入有丝分裂，导致染色体分离缺陷和细胞死亡。总的来说，这些发现提供了对 SUMO 驱动途径的机制见解，这些途径是复制独立 DPC 分辨率的基础，并强调了它们在维持染色体稳定性和细胞适应性方面的关键重要性。