title: Evidence for transcription attenuation rendering cryptic a sigmaS-dependent promoter of the osmotically regulated proU operon of Salmonella typhimurium.
abstract: The osmotically regulated proU locus in Escherichia coli has two promoters, P1 and P2, that are recognized, respectively, by the sigmaS- and sigma70-bearing RNA polymerase holoenzymes. However, the equivalent of the P1 promoter does not appear to exist in Salmonella typhimurium. We demonstrate in this study that wild-type S. typhimurium has a cryptic P1 promoter that is recognized by sigmaS RNA polymerase in vitro and that a 22-bp deletion from +63 to +84 (relative to the start site of transcription) confers sigmaS-dependent in vivo expression of a reporter gene fusion to P1. Primer extension analysis of RNA isolated from cells carrying the wild-type and mutant S. typhimurium proU constructs indicated that a primer which hybridizes proximal to +60 is able to detect P1-initiated transcripts from both constructs but a primer which hybridizes distal to +85 is able to do so only from the latter. Our results suggest that the sigmaS-controlled proU P1 promoter in S. typhimurium may be rendered cryptic because of factor-dependent transcription attenuation within a short distance downstream of the promoter start site.
authors.affiliation: Centre for Cellular & Molecular Biology, Hyderabad, India.
authors.forename: K
authors.initials: K
authors.lastname: Rajkumari
authors.forename: A
authors.initials: A
authors.lastname: Ishihama
authors.forename: J
authors.initials: J
authors.lastname: Gowrishankar
mesh_terms: D019677:Artificial Gene Fusion; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D007763:Lac Operon; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics*; D012486:Salmonella typhimurium / Q000235:genetics*; D017384:Sequence Deletion; D012808:Sigma Factor / Q000235:genetics*; D037941:Silencer Elements, Transcriptional; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D012097:Repressor Proteins; D012808:Sigma Factor; C095098:proU silencer; C069567:sigma factor KatF protein, Bacteria