title: Identification of DNA topoisomerases involved in immediate and transient DNA relaxation induced by heat shock in Escherichia coli.
abstract: The linking number of plasmid DNA in exponentially growing Escherichia 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 a topA 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 the topA mutant and the reaction was resistant to nalidixic acid in a topA mutant carrying, in addition, the nalA26 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.
authors.affiliation: Department of Microbiology, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Ogata
authors.forename: T
authors.initials: T
authors.lastname: Mizushima
authors.forename: K
authors.initials: K
authors.lastname: Kataoka
authors.forename: T
authors.initials: T
authors.lastname: Miki
authors.forename: K
authors.initials: K
authors.lastname: Sekimizu
mesh_terms: D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D004269:DNA, Bacterial / Q000737:chemistry* / Q000187:drug effects; D004278:DNA, Superhelical / Q000737:chemistry* / Q000187:drug effects; D004587:Electrophoresis, Agar Gel; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D006360:Heat-Shock Proteins / Q000378:metabolism*; D009268:Nalidixic Acid / Q000494:pharmacology; D009690:Nucleic Acid Conformation / Q000187:drug effects; D010093:Oxolinic Acid / Q000494:pharmacology; D010957:Plasmids; D059004:Topoisomerase I Inhibitors; D059005:Topoisomerase II Inhibitors
chemical_list: D004269:DNA, Bacterial; D004278:DNA, Superhelical; D006360:Heat-Shock Proteins; D059004:Topoisomerase I Inhibitors; D059005:Topoisomerase II Inhibitors; D009268:Nalidixic Acid; D004264:DNA Topoisomerases, Type I; D004250:DNA Topoisomerases, Type II; D010093:Oxolinic Acid