Salmonella enterica response regulator SsrB relieves H-NS silencing by displacing H-NS bound in polymerization mode and directly activates transcription

Don Walthers, You Li, Yingjie Liu, Ganesh Anand, Jie Yan, Linda J. Kenney

Research output: Contribution to journalArticlepeer-review

63 Scopus citations

Abstract

The response regulator SsrB activates expression of genes encoded within and outside of a pathogenicity island (SPI-2), which is required for systemic infection of Salmonella. SsrB binds upstream of the sifA, sifB, and sseJ effector genes and directly regulates transcription. SsrB also relieves gene silencing by the nucleoid protein H-NS. Single molecule experiments with magnetic tweezers demonstrated that SsrB displaces H-NS from DNA only when it is bound in a polymerization (stiffening) mode and not when H-NS is bound to DNA in the bridging mode. Thus, in contrast to previous views, the polymerization binding mode of H-NS is the relevant form for counter-silencing by SsrB. Our results reveal that response regulators can directly activate transcription and also relieve H-NS silencing. This study adds to the repertoire of mechanisms by which NarL/FixJ subfamily members regulate transcription. Because SsrB-dependent promoters are diversely organized, additional mechanisms of transcriptional activation at other loci are likely.

Original languageEnglish (US)
Pages (from-to)1895-1902
Number of pages8
JournalJournal of Biological Chemistry
Volume286
Issue number3
DOIs
StatePublished - Jan 21 2011

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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