The H-NS-like protein StpA represses the RpoS (sigma 38) regulon during exponential growth of Salmonella Typhimurium.
StpA is a paralogue of the nucleoid-associated protein H-NS that is conserved in a range of enteric bacteria and had no known function in Salmonella Typhimurium. We show that 5% of the Salmonella genome is regulated by StpA, which contrasts with the situation in Escherichia coli where deletion of stpA only had minor effects on gene expression. The StpA-dependent genes of S. Typhimurium are a specific subset of the H-NS regulon that are predominantly under the positive control of sigma(38) (RpoS), CRP-cAMP and PhoP. Regulation by StpA varied with growth phase; StpA controlled sigma(38) levels at mid-exponential phase by preventing inappropriate activation of sigma(38) during rapid bacterial growth. In contrast, StpA only activated the CRP-cAMP regulon during late exponential phase. ChIP-chip analysis revealed that StpA binds to PhoP-dependent genes but not to most genes of the CRP-cAMP and sigma(38) regulons. In fact, StpA indirectly regulates sigma(38)-dependent genes by enhancing sigma(38) turnover by repressing the anti-adaptor protein rssC. We discovered that StpA is essential for the dynamic regulation of sigma(38) in response to increased glucose levels. Our findings identify StpA as a novel growth phase-specific regulator that plays an important physiological role by linking sigma(38) levels to nutrient availability.
Lucchini
Sacha
S
Institute of Food Research, Colney Lane, Norwich, NR4 7UA, UK. sacha.lucchini@bbsrc.ac.uk
McDermott
Paul
P
Thompson
Arthur
A
Hinton
Jay C D
JC
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005947:Glucose / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism*; D055550:Protein Stability; D018085:Regulon; D012486:Salmonella typhimurium / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D012808:Sigma Factor / Q000378:metabolism*
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D012808:Sigma Factor; C090104:StpA protein, E coli; C548413:StpA protein, Salmonella typhimurium; C069567:sigma factor KatF protein, Bacteria; D005947:Glucose