The H-NS-like protein StpA represses the RpoS (sigma 38) regulon during exponential growth of Salmonella Typhimurium

Mol Microbiol. 2009 Dec;74(5):1169-86. doi: 10.1111/j.1365-2958.2009.06929.x. Epub 2009 Oct 19.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / metabolism*
  • Cell Wall / metabolism
  • Cloning, Molecular
  • DNA-Binding Proteins / metabolism*
  • Escherichia coli / genetics
  • Escherichia coli / growth & development
  • Escherichia coli / metabolism
  • Escherichia coli Proteins / metabolism
  • Gene Expression Regulation, Bacterial*
  • Glucose / metabolism
  • Molecular Chaperones / metabolism*
  • Protein Stability
  • Regulon*
  • Salmonella typhimurium / cytology
  • Salmonella typhimurium / genetics
  • Salmonella typhimurium / growth & development
  • Salmonella typhimurium / metabolism*
  • Sigma Factor / metabolism*

Substances

  • Bacterial Proteins
  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • Molecular Chaperones
  • Sigma Factor
  • StpA protein, E coli
  • StpA protein, Salmonella typhimurium
  • sigma factor KatF protein, Bacteria
  • Glucose