Dynamic state of DNA topology is essential for genome condensation in bacteria
Dynamic state of DNA topology is essential for genome condensation in bacteria
复制标题
DOI：
10.1038/sj.emboj.7601414
复制
发表时间：
2006-11-29
期刊：
影响因子：
11.4
通讯作者：
Takeyasu, Kunio
中科院分区：
文献类型：
--
作者：
Ohniwa, Ryosuke L.;Morikawa, Kazuya;Takeyasu, Kunio
在细菌中，Dps是响应环境胁迫而形成浓缩类核的关键蛋白之一。在本研究中，我们发现Dps的表达和类核凝聚在大肠杆菌中不是简单的相关，而Fis，这是一种大肠杆菌。大肠杆菌（γ-变形菌）特异性的类核蛋白，干扰Dps依赖的类核凝聚。原子力显微镜和北方印迹分析表明，Fis的抑制作用是由于抑制拓扑异构酶I（Topo I）和DNA旋转酶的表达。在Delta fis菌株中，发现topA和gyrA/B基因均上调。Topo I和DNA旋转酶的过表达增强了Dps存在下的类核凝聚。使用细胞提取物的DNA拓扑分析表明，Dfis和Topo I-/DNA回旋酶过表达菌株的提取物，而不是野生型提取物，使种群向松弛形式转移。这些结果表明，DNA的拓扑结构是动态可转换的，拓扑结构的控制是重要的Dps诱导的类核缩合。
In bacteria, Dps is one of the critical proteins to build up a condensed nucleoid in response to the environmental stresses. In this study, we found that the expression of Dps and the nucleoid condensation was not simply correlated in Escherichia coli, and that Fis, which is an E. coli (gamma-Proteobacteria)-specific nucleoid protein, interfered with the Dps-dependent nucleoid condensation. Atomic force microscopy and Northern blot analyses indicated that the inhibitory effect of Fis was due to the repression of the expression of Topoismerase I (Topo I) and DNA gyrase. In the Delta fis strain, both topA and gyrA/B genes were found to be upregulated. Overexpression of Topo I and DNA gyrase enhanced the nulceoid condensation in the presence of Dps. DNA-topology assays using the cell extract showed that the extracts from the Dfis and Topo I-/DNA gyrase-overexpressing strains, but not the wild-type extract, shifted the population toward relaxed forms. These results indicate that the topology of DNA is dynamically transmutable and that the topology control is important for Dps-induced nucleoid condensation.