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- Title
Dual regulation of the paraquat-inducible gene pqi-5 by SoxS and RpoS in Escherichia coli.
- Authors
Young-Sang Koh; Jung-Hye Roe
- Abstract
The <em>pqi-5</em> gene, producing a probable membrane protein of unknown function, has been reported to be a member of the <em>soxRS</em> regulon. The SoxRS-dependent induction of <em>pqi-5</em> by paraquat occurs only during the exponential phase. The expression of <em>pqi-5</em> increased in the absence of paraquat during the stationary phase or under conditions of carbon or phosphate starvation. This increase was regulated at the transcriptional level by RpoS (σS), which recognized the second promoter (P2) approx. 5 nucleotides upstream from the promoter (PI) used at the exponential phase. Studies with a series of 5′ deletions revealed that the paraquat-responsive element resides between -52 and -42 nucleotides upstream from the PI start site, whose nucleotide sequence matches closely to other SoxS-binding sequences. The stationary-phase induction required sequences up to position -42, which correspond to the 5′ border of the putative -35 hexamer for the P2 promoter. The binding of the purified SoxS protein to the <em>pqi-5</em> promoter upstream sequences was demonstrated by gel mobility-shift and DNase I protection assays. The transcription from Pi promoter by EσD was activated by purified SoxS <em>in vitro</em>, as was observed <em>in vivo</em>. The dual regulation of <em>pqi-5</em> by SoxS at the exponential phase and RpoS at the stationary phase is the first to be reported among the members of the <em>soxRS</em> regulon, suggesting that this gene might indeed play some role under stressful conditions.
- Subjects
PARAQUAT; ESCHERICHIA coli; GENE expression; GENETIC regulation; GENETIC transcription
- Publication
Molecular Microbiology, 1996, Vol 22, Issue 1, p53
- ISSN
0950-382X
- Publication type
Article
- DOI
10.1111/j.1365-2958.1996.tb02655.x