The small RNA, DsrA, is essential for the low temperature expression of RpoS during exponential growth in Escherichia coli

EMBO J. 1996 Aug 1;15(15):3993-4000.


dsrA encodes a small, untranslated RNA. When over-expressed, DsrA antagonizes the H-NS-mediated silencing of numerous promoters. Cells devoid of DsrA grow normally and show little change in the expression of a number of H-NS-silenced genes. Expression of a transcriptional fusion of lacZ to dsrB, the gene next to dsrA, is significantly lower in cells carrying mutations in dsrA. All expression of beta-galactosidase from the dsrB::lacZ fusion is also dependent on the stationary phase sigma factor, RpoS. DsrA RNA was found to regulate dsrB::lacZ indirectly, by modulating RpoS synthesis. Levels of RpoS protein are substantially lower in a dsrA mutant, both in stationary and exponential phase cells. Mutations in dsrA decrease the expression of an RpoS::LacZ translational fusion, but not a transcriptional fusion, suggesting that DsrA is acting after transcription initiation. While RpoS expression is very low in exponential phase at temperatures of 30 degrees C and above, at 20 degrees C there is substantial synthesis of RpoS during exponential growth, all dependent on DsrA RNA. dsrA expression is also increased at low temperatures. These results suggest a new role for RpoS during exponential growth at low temperatures, mediated by DsrA.

MeSH terms

  • Bacterial Proteins / biosynthesis
  • Bacterial Proteins / genetics*
  • Blotting, Western
  • Escherichia coli / genetics*
  • Escherichia coli / growth & development
  • Gene Expression Regulation, Bacterial*
  • Lac Operon
  • Plasmids / metabolism
  • RNA, Bacterial / metabolism
  • RNA, Small Nuclear / metabolism*
  • Sigma Factor / biosynthesis
  • Sigma Factor / genetics*
  • Temperature


  • Bacterial Proteins
  • RNA, Bacterial
  • RNA, Small Nuclear
  • Sigma Factor
  • sigma factor KatF protein, Bacteria