title: Suppression of leu-500 mutation in topA+ Salmonella typhimurium strains. The promoter relay at work.
abstract: Suppression of leu-500 mutation in Salmonella typhimurium topA- strains has been one of the most fascinating examples for the DNA supercoiling effect on transcription initiation control. Previous studies have indicated possible involvement of transcription-driven DNA supercoiling in the activation of the leu-500 promoter in topA- strains. Our recent studies have shown that ilvIH transcription activity located 1.9 kilobase pairs upstream is the initial supercoiling signal for leu-500 activation via a promoter relay mechanism. In the present communication, we show that the ilvIH transcription activity-initiated promoter relay can result in leu-500 activation in topA+ strains. In addition, suppression of the chromosomal leu-500 mutation correlates with the transcription activities of ilvIH and leuO rather than the TopA level in the topA+ strain. It appears that the leu-500 suppression in a topA- strain is due to the constant ilvIH transcription activity.
authors.affiliation: Department of Pharmacology, School of Medicine, Wayne State University, Detroit, Michigan 48201, USA.
authors.forename: M
authors.initials: M
authors.lastname: Fang
authors.forename: H Y
authors.initials: HY
authors.lastname: Wu
mesh_terms: D002876:Chromosomes, Bacterial; D007930:Leucine / Q000235:genetics*; D009154:Mutation; D010957:Plasmids; D011401:Promoter Regions, Genetic; D012486:Salmonella typhimurium / Q000235:genetics*
chemical_list: D007930:Leucine