title: Effect of the deletion of the sigma 32-dependent promoter (P1) of the Escherichia coli topoisomerase I gene on thermotolerance.
abstract: Topoisomerase I and DNA gyrase are the major topoisomerase activities responsible for the regulation of DNA supercoiling in the bacterium Escherichia coli. The P1 promoter of topA has previously been shown to be a delta 32-dependent heat-shock promoter. A mutant strain with a deletion of P1 was constructed. This mutant is > 10-fold more sensitive to heat treatment (52 degrees C) than the wild type. After brief treatment at 42 degrees C, wild-type Escherichia coli acquires an enhanced resistance to the effects of a subsequent 52 degrees C treatment. This is not the case for the P1 deletion mutant, which, and under these conditions, is about 100-fold less thermotolerant than the wild type. The presence of a plasmid expressing topoisomerase I restored the heat-survival level of the mutant to that of the wild type. During heat shock, the superhelical density of a plasmid with the heat-inducible rpoD promoter is increased in the P1 deletion mutant. We also note that the pulse-labelling pattern of proteins at 42 C (displayed on SDS-polyacrylamide gels) is different in the mutant, and, most notably, the amounts of DnaK and of GroEL protein are reduced. A model is proposed in order to unify these observations.
authors.affiliation: Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla 10595, USA.
authors.forename: H
authors.initials: H
authors.lastname: Qi
authors.forename: R
authors.initials: R
authors.lastname: Menzel
authors.forename: Y C
authors.initials: YC
authors.lastname: Tse-Dinh
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis; D001483:Base Sequence; D004264:DNA Topoisomerases, Type I / Q000235:genetics*; D004269:DNA, Bacterial / Q000032:analysis; D004278:DNA, Superhelical / Q000032:analysis; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics; D006360:Heat-Shock Proteins / Q000502:physiology*; D006358:Hot Temperature; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012329:RNA, Bacterial / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D017384:Sequence Deletion; D012808:Sigma Factor / Q000235:genetics / Q000502:physiology*; D014157:Transcription Factors; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004278:DNA, Superhelical; D006360:Heat-Shock Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012808:Sigma Factor; D014157:Transcription Factors; C069774:heat-shock sigma factor 32; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases; D004264:DNA Topoisomerases, Type I