Topoisomerase I (TOP1) controls the topological state of DNA during DNA replication, and its dysfunction due to treatment with an inhibitor, such as camptothecin (CPT), causes replication arrest and cell death. Although CPT has excellent cytotoxicity, it has the disadvantage of instability under physiological conditions. Therefore, new types of TOP1 inhibitor have attracted particular attention. Here, we characterised the effect of a non-camptothecin inhibitor, Genz-644282 (Genz). First, we found that treatment with Genz showed cytotoxicity by introducing double-strand breaks (DSBs), which was suppressed by co-treatment with aphidicolin. Genz-induced DSB formation required the functions of TOP1. Next, we explored the advantages of Genz over CPT and found it was effective against CPT-resistant TOP1 carrying either N722S or N722A mutation. The effect of Genz was also confirmed at the cellular level using a CPT-resistant cell line carrying N722S mutation in the TOP1 gene. Moreover, we found arginine residue 364 plays a crucial role for the binding of Genz. Because tyrosine residue 723 is the active centre for DNA cleavage and re-ligation by TOP1, asparagine residue 722 plays crucial roles in the accessibility of the drug. Here, we discuss the mechanism of action of Genz on TOP1 inhibition.

拓扑异构酶 I (TOP1) 在 DNA 复制过程中控制 DNA 的拓扑状态，并且由于使用抑制剂（如喜树碱 (CPT)）处理而导致的功能障碍导致复制停滞和细胞死亡。CPT虽然具有优异的细胞毒性，但在生理条件下存在不稳定的缺点。因此，新型TOP1抑制剂备受关注。在这里，我们描述了一种非喜树碱抑制剂 Genz-644282 (Genz) 的作用。首先，我们发现 Genz 处理通过引入双链断裂 (DSB) 显示细胞毒性，而双链断裂 (DSB) 可通过与 aphidicolin 共同处理而抑制。Genz 诱导的 DSB 形成需要 TOP1 的功能。接下来，我们探索了 Genz 相对于 CPT 的优势，发现它对携带 N722S 或 N722A 突变的 CPT 抗性 TOP1 有效。TOP1基因。此外，我们发现精氨酸残基 364 对 Genz 的结合起着至关重要的作用。因为酪氨酸残基 723 是 TOP1 切割 DNA 和重新连接的活性中心，所以天冬酰胺残基 722 在药物的可及性中起着至关重要的作用。在这里，我们讨论了 Genz 对 TOP1 抑制的作用机制。