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Identification of DNA topoisomerases involved in immediate and transient DNA relaxation induced by heat shock inEscherichia coli
Authors:Yasuyuki Ogata   Tohru Mizushima   Kazuhiro Kataoka   Takeyoshi Miki  Kazuhisa Sekimizu
Affiliation:(1) Department of Microbiology, Faculty of Pharmaceutical Sciences, Kyushu University, 812 Maidashi, Higashi-ku, Fukuoka, Japan
Abstract:The linking number of plasmid DNA in exponentially growingEscherichia coli increases immediately and transiently after heat shock. The purpose of this study was to search for DNA topoisomerases that catalyze this relaxation of DNA. Neither introduction of atopA deletion mutation nor treatment of cells with DNA gyrase inhibitors affected the DNA relaxation induced by heat shock. Thus, DNA topoisomerase I and DNA gyrase are apparently not involved in the process. However, the reaction was inhibited by nalidixic acid or by oxolinic acid in thetopA mutant and the reaction was resistant to nalidixic acid in atopA mutant carrying, in addition, thenalA26 mutation. These results are interpreted as indicating that both DNA topoisomerase I and DNA gyrase are involved in the DNA relaxation induced by heat shock.
Keywords:Heat shock  DNA relaxation  topA  DNA topoisomerase I  DNA gyrase
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