DNA topoisomerase II (TOP2) poisons induce protein-DNA crosslinks termed TOP2-DNA covalent complexes, in which TOP2 remains covalently bound to each end of an enzyme-induced double-strand DNA break (DSB) via a 5′-phosphotyrosyl bond. Repair of the enzyme-induced DSB first requires the removal of the TOP2 protein adduct, which, among other mechanisms, can be accomplished through the proteasomal degradation of TOP2. VCP/p97 is a AAA ATPase that utilizes energy from ATP hydrolysis to unfold protein substrates, which can facilitate proteasomal degradation by extracting target proteins from certain cellular structures (such as chromatin) and/or by aiding their translocation into the proteolytic core of the proteasome. In this study, we show that inhibition of VCP/p97 leads to the prolonged accumulation of etoposide-induced TOP2A and TOP2B complexes in a manner that is epistatic with the proteasomal pathway. VCP/p97 inhibition also reduces the etoposide-induced phosphorylation of histone H2A.X, indicative of fewer DSBs. This suggests that VCP/p97 is required for the proteasomal degradation of TOP2-DNA covalent complexes and is thus likely to be an important mediator of DSB repair after treatment with a TOP2 poison.

中文翻译：

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VCP/p97 在药物稳定的 TOP2-DNA 共价复合物加工中的作用

DNA 拓扑异构酶 II (TOP2) 毒物诱导蛋白质-DNA 交联，称为 TOP2-DNA 共价复合物，其中 TOP2 通过 5'-磷酸酪氨酰键与酶诱导的双链 DNA 断裂 (DSB) 的每个末端共价结合。酶诱导的 DSB 的修复首先需要去除 TOP2 蛋白加合物，除其他机制外，这可以通过 TOP2 的蛋白酶体降解来完成。VCP/p97 是一种 AAA ATPase，它利用来自 ATP 水解的能量来展开蛋白质底物，它可以通过从某些细胞结构（如染色质）中提取靶蛋白和/或帮助它们易位到蛋白酶体的蛋白水解核心中来促进蛋白酶体降解. 在这项研究中，我们表明，VCP/p97 的抑制导致依托泊苷诱导的 TOP2A 和 TOP2B 复合物以与蛋白酶体途径上位的方式长期积累。VCP/p97 抑制还降低了依托泊苷诱导的组蛋白 H2A.X 磷酸化，表明 DSB 较少。这表明 VCP/p97 是 TOP2-DNA 共价复合物的蛋白酶体降解所必需的，因此可能是用 TOP2 毒物处理后 DSB 修复的重要介质。