Article
- The EMBO Journal (2006) 25, 5591 - 5602
- doi:10.1038/sj.emboj.7601414
Published online: 9 November 2006
Subject Categories:
Dynamic state of DNA topology is essential for genome condensation in bacteria
Ryosuke L Ohniwa1, Kazuya Morikawa2, Joongbaek Kim1, Toshiko Ohta2, Akira Ishihama3, Chieko Wada1 and Kunio Takeyasu1
- Laboratory of Plasma Membrane and Nuclear Signaling, Kyoto University Graduate School of Biostudies, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, Japan
- Institute of Basic Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tennoh-dai, Tsukuba, Japan
- Department of Frontier Bioscience, Hosei University, Koganei, Tokyo, Japan
Correspondence to:
Ryosuke L Ohniwa, Laboratory of Plasma Membrane and Nuclear Signaling, Kyoto University Graduate School of Biostudies, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan. Tel./Fax: +81 75 753 7905; E-mail: ohniwa@lif.kyoto-u.ac.jp
Received 20 April 2006; Accepted 6 October 2006
Abstract
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 
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 fis 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.
Keywords:
- atomic force microscopy,
- Dps,
- Fis,
- nucleoid condensation,
- topology control
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