Distribution of gyrase and topoisomerase IV on bacterial nucleoid: implications for nucleoid organization.
Distribution of gyrase and topoisomerase IV on bacterial nucleoid: implications for nucleoid organization.
复制标题
DOI：
10.1093/nar/gkl392
复制
发表时间：
2006
影响因子：
14.9
通讯作者：
Li TK
中科院分区：
文献类型：
--
作者：
Hsu YH;Chung MW;Li TK
我们通过研究细菌II型拓扑异构酶(Topo II)的分布，探索了大肠杆菌中类核DNA环的存在。诺氟沙星诱导类核高分子量(HMW)DNA断裂，这一事件使人想起拓扑异构酶II(TOP2)介导的真核细胞染色体DNA环的切除。诺氟沙星诱导的HMW DNA片段大小受细菌转录、翻译和生长阶段的影响。以下观察结果支持细菌Topo II参与这些HMW DNA片段的产生：(I)切除的环大小的DNA片段与蛋白质共价连接；(Ii)诺氟沙星诱导的DNA环的切除是高度可逆的；(Iii)香豆素A1拮抗诺氟沙星诱导的DNA环的切除；(Iv)这种拮抗作用在导致香豆素耐药性的旋转酶或Topo IV突变体中减弱，以及(V)诺氟沙星诱导的可逆的旋转酶介导的DNA切割。重要的是，对香豆素和/或喹诺酮类耐药突变株的研究表明，DNA旋转酶而不是拓扑异构酶IV在产生环状大小的HMW DNA片段中起主要作用。综上所述，我们的研究表明，Topo II在原核细胞中DNA超螺旋环域的排列中具有潜在的作用。
We explored the existence of nucleoid DNA loops in Escherichia coli by studying the distribution of bacterial type II topoisomerases (Topo IIs). Norfloxacin-induced high molecular weight (HMW) DNA fragmentation of nucleoid, an event reminiscent of the excision of eukaryotic chromosomal DNA loops mediated by topoisomerase II (TOP2). The size of the HMW DNA fragments induced by norfloxacin was affected by transcription, translation and growth phases of bacteria. The involvement of bacterial Topo IIs in the generation of these HMW DNA fragments is supported by the following observations: (i) the excised loop-sized DNA fragments were covalently linked to proteins; (ii) the norfloxacin-induced excision of DNA loops was highly reversible; (iii) coumermycin A1 antagonized the excision of DNA loops induced by norfloxacin; (iv) this antagonistic effect was reduced in either gyrase or topo IV mutants conferring coumarin resistance and (v) norfloxacin-induced reversible, gyrase-mediated DNA cleavage in vitro. Importantly, studies on coumarin- and/or quinolone-resistant mutant strains showed that DNA gyrase, rather than topoisomerase IV, plays the major role in the generation of loop-sized HMW DNA fragments. In sum, our study suggests a potential role of Topo IIs in the arrangement of DNA supercoiling loop domains in prokaryotic cells.