The RpoS sigma factor relieves H-NS-mediated transcriptional repression of csgA, the subunit gene of fibronectin-binding curli in Escherichia coli.
Curli encoded by the curlin subunit gene, csgA, are fibronectin- and laminin-binding fibres expressed by many natural Escherichia coli and E. coli K-12 strains in response to low temperature, low osmolarity and stationary-phase growth conditions. Curli expression is dependent on RpoS, a sigma factor that controls many stationary phase-inducible genes. Many commonly used K-12 strains carry an amber mutation in rpoS. Strains able to form curli carry an amber suppressor whereas curli-negative E. coli K-12 strains, in general, are sup0. Introduction of SupD, SupE, or supF suppressors into sup0 strains resulted in expression of temperature-regulated curli. In curli-deficient, RpoS- E. coli K-12 strains, csgA is transcriptionally activated by mutations in hns, which encodes the histone-like protein H-NS. Curli expression, fibronectin binding, and csgA transcription remain temperature- and osmoregulated in such double mutants. Our data suggest that RpoS+ strains, and hence curli-proficient strains of E. coli K-12, are relieved for the transcriptional repression mediated by the H-NS protein upon accumulating RpoS as cells reach stationary phase.[1]References
- The RpoS sigma factor relieves H-NS-mediated transcriptional repression of csgA, the subunit gene of fibronectin-binding curli in Escherichia coli. Olsén, A., Arnqvist, A., Hammar, M., Sukupolvi, S., Normark, S. Mol. Microbiol. (1993) [Pubmed]
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