title: Regulatory role of RsgI in sigI expression in Bacillus subtilis.
abstract: The sigma gene, sigI, of Bacillus subtilis belongs to the group IV heat-shock response genes and has many orthologues in the bacterial phylum Firmicutes. The B. subtilis sigI gene is considered to constitute an operon with rsgI (regulation of sigI, formerly ykrI). As little is known about either the structure and function of the sigI-rsgI operon or the SigI regulons, the role of RsgI in heat-inducible transcription of the sigI-rsgI operon was investigated, using Northern analysis and a heat-stable beta-galactosidase reporter assay. Heat-inducible, SigI-dependent transcription of the sigI-rsgI operon was stimulated greatly by disrupting rsgI. Yeast two-hybrid analysis showed direct interaction between the N-terminal portion of the presumed RsgI protein and SigI. Without RsgI function, induction of transcription of the sigI-rsgI operon upon transient heat stress depended on dnaK activity. However, transcription of the operon was induced during growth at prolonged higher temperature even without DnaK function. Without RsgI function, sigI-rsgI operon transcription was induced after the end of growth independent of any temperature shift in a sporulation medium and toward the end of growth in a rich complex medium. Furthermore, glucose addition resulted in a strong suppression of sigI-rsgI transcription. Therefore it is hypothesized that transcription of the sigI-rsgI operon of B. subtilis is negatively regulated by the putative transmembrane protein RsgI, which moderates SigI's sensitivity to heat shock or nutritional stress.
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Science, Saitama University, Saitama 338-8570, Saitama, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Asai
authors.forename: Takafumi
authors.initials: T
authors.lastname: Ootsuji
authors.forename: Kazue
authors.initials: K
authors.lastname: Obata
authors.forename: Takashi
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Yasutaro
authors.initials: Y
authors.lastname: Fujita
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Sadaie
mesh_terms: D001412:Bacillus subtilis / Q000235:genetics*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D001483:Base Sequence; D015536:Down-Regulation; D006360:Heat-Shock Proteins / Q000235:genetics*; D018869:Heat-Shock Response; D008969:Molecular Sequence Data; D009876:Operon / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D012808:Sigma Factor / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D006360:Heat-Shock Proteins; C422477:SigI protein, Bacillus subtilis; D012808:Sigma Factor