The widely used quinolone antibiotics act by trapping prokaryotic type IIA topoisomerases, resulting in irreversible topoisomerase cleavage complexes (TOPcc). Whereas the excision repair pathways of TOPcc in eukaryotes have been extensively studied, it is not known whether equivalent repair pathways for prokaryotic TOPcc exist. By combining genetic, biochemical, and molecular biology approaches, we demonstrate that exonuclease VII (ExoVII) excises quinolone-induced trapped DNA gyrase, an essential prokaryotic type IIA topoisomerase. We show that ExoVII repairs trapped type IIA TOPcc and that ExoVII displays tyrosyl nuclease activity for the tyrosyl-DNA linkage on the 5′-DNA overhangs corresponding to trapped type IIA TOPcc. ExoVII-deficient bacteria fail to remove trapped DNA gyrase, consistent with their hypersensitivity to quinolones. We also identify an ExoVII inhibitor that synergizes with the antimicrobial activity of quinolones, including in quinolone-resistant bacterial strains, further demonstrating the functional importance of ExoVII for the repair of type IIA TOPcc.

广泛使用的喹诺酮类抗生素通过捕获原核 IIA 型拓扑异构酶发挥作用，产生不可逆的拓扑异构酶裂解复合物 (TOPcc)。尽管真核生物中 TOPcc 的​​切除修复途径已被广泛研究，但尚不清楚原核生物 TOPcc 是否存在等效的修复途径。通过结合遗传、生化和分子生物学方法，我们证明外切核酸酶 VII (ExoVII) 可以切除喹诺酮诱导的捕获 DNA 促旋酶，这是一种必需的原核 IIA 型拓扑异构酶。我们显示 ExoVII 修复了被捕获的 IIA 型 TOPcc，并且 ExoVII 显示了酪氨酰核酸酶活性，用于对应于被捕获的 IIA 型 TOPcc 的​​ 5'-DNA 突出端上的酪氨酰-DNA 键。ExoVII 缺陷细菌无法去除捕获的 DNA 旋转酶，这与它们对喹诺酮类药物的超敏反应一致。