• The protease WSS1A is an important factor in the repair of DNA-protein crosslinks in plants.
• Here we show that the loss of WSS1A leads to a reduction of 45S rDNA repeats and chromosomal fragmentation in Arabidopsis. Moreover, in the absence of any factor of the RTR (RECQ4A/TOP3α/RMI1/2) complex, which is involved in the dissolution of DNA replication intermediates, WSS1A becomes essential for viability.
• If WSS1A loss is combined with loss of the classical (c) or alternative (a) nonhomologous end joining (NHEJ) pathways of double-strand break (DSB) repair, the resulting mutants show proliferation defects and enhanced chromosome fragmentation, which is especially aggravated in the absence of aNHEJ. This indicates that WSS1A is involved either in the suppression of DSB formation or in DSB repair itself. To test the latter we induced DSB by CRISPR/Cas9 at different loci in wild-type and mutant cells and analyzed their repair by deep sequencing. However, no change in the quality of the repair events and only a slight increase in their quantity was found.
• Thus, by removing complex DNA-protein structures, WSS1A seems to be required for the repair of replication intermediates which would otherwise be resolved into persistent DSB leading to genome instability.

中文翻译：

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DNA依赖性蛋白酶AtWSS1A抑制复制过程中持续的双链断裂形成

• 蛋白酶WSS1A是修复植物中DNA-蛋白质交联的重要因子。
• 在这里，我们表明 WSS1A 的缺失导致拟南芥中 45S rDNA 重复和染色体片段化的减少。此外，在没有参与 DNA 复制中间体溶解的 RTR (RECQ4A/TOP3α/RMI1/2) 复合物的任何因素的情况下，WSS1A 对生存能力至关重要。
• 如果 WSS1A 缺失与双链断裂 (DSB) 修复的经典 (c) 或替代 (a) 非同源末端连接 (NHEJ) 途径的缺失相结合，则产生的突变体显示出增殖缺陷和增强的染色体片段化，这种情况尤其严重在没有 aNHEJ 的情况下。这表明 WSS1A 参与抑制 DSB 形成或参与 DSB 修复本身。为了测试后者，我们通过 CRISPR/Cas9 在野生型和突变细胞的不同位点诱导 DSB，并通过深度测序分析了它们的修复。但是，维修事件的质量没有变化，只是数量略有增加。
• 因此，通过去除复杂的 DNA-蛋白质结构，WSS1A 似乎是修复复制中间体所必需的，否则这些中间体将被分解为持久的 DSB，从而导致基因组不稳定。