Ishida R, Nishizawa M, Fukami K, Maekawa K, Takahashi T, Nishimoto T
Somat Cell Mol Genet. 1987 Jan;13(1):11-20. doi: 10.1007/BF02422295.
We isolated two novobiocin-resistant mutants which were stable and approximately three and four times more resistant than the parent cells to novobiocin. Both mutants (Novr A2, Novr A41) were more sensitive than the wild-type cells to nalidixic acid, and cold sensitive for cell growth. When we isolated derivatives of Novr A2 and Novr A41 cells which are resistant to nalidixic acid, those are found to be phenotypically reverted to novobiocin sensitivity like wild-type cells, thereby suggesting the relationship between the targets for novobiocin and for nalidixic acid. But the cold sensitivity did not always revert to wild type, with accompanying resistance to nalidixic acid. The DNA and RNA syntheses of Novr mutants were more resistant to novobiocin but more sensitive to nalidixic acid, than those of wild-type cells. However, in vitro assays of wild-type and Novr cell extracts were unable to demonstrate any differences in the sensitivity of topoisomerase II activity to inhibition by novobiocin. While the targets of novobiocin and nalidixic acid show a mutual interaction in vivo and play a role in DNA replication and transcription, our results suggest that these targets are probably not topoisomerase II.
我们分离出了两个新生霉素抗性突变体，它们很稳定，对新生霉素的抗性约为亲本细胞的三到四倍。两个突变体（Novr A2、Novr A41）对萘啶酸比野生型细胞更敏感，且对细胞生长有冷敏感性。当我们分离出对萘啶酸有抗性的Novr A2和Novr A41细胞的衍生物时，发现它们在表型上恢复为对新生霉素敏感，如同野生型细胞，从而表明新生霉素和萘啶酸的作用靶点之间存在关联。但是伴随对萘啶酸的抗性，冷敏感性并不总是恢复到野生型。与野生型细胞相比，Novr突变体的DNA和RNA合成对新生霉素更具抗性，但对萘啶酸更敏感。然而，对野生型和Novr细胞提取物的体外测定未能证明拓扑异构酶II活性对新生霉素抑制的敏感性存在任何差异。虽然新生霉素和萘啶酸的作用靶点在体内表现出相互作用，并在DNA复制和转录中发挥作用，但我们的结果表明这些靶点可能不是拓扑异构酶II。
