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. 1998 May 1;17(9):2629–2636. doi: 10.1093/emboj/17.9.2629

The redox-regulated SoxR protein acts from a single DNA site as a repressor and an allosteric activator.

E Hidalgo 1, V Leautaud 1, B Demple 1
PMCID: PMC1170604  PMID: 9564045

Abstract

The SoxR protein of Escherichia coli responds to redox signals by activating the transcription of soxS, which encodes another transcription activator that directly stimulates oxidative stress genes. We show here that transcription of the soxR gene, which is positioned head-to-head with soxS in the chromosome, initiates in the intergenic region and is itself repressed by SoxR protein in in vitro transcription experiments. Analysis of single-copy operon fusions to soxR, combined with the results of Northern blotting experiments, verified this regulation and the transcription start site in vivo. The structure of the overlapping promoters is such that the single SoxR-binding site is located in the -10/-35 spacer of the soxS promoter, but just downstream of the -10 element of the soxR promoter. Activated and non-activated SoxR bind this site equally well, exerting nearly constant repression of soxR; activated SoxR simultaneously stimulates the soxS promoter >/=30-fold. The functional soxR promoter depresses soxS transcription when SoxR is not activated and enhances soxS transcription when SoxR is activated, as shown by comparing the expression of soxS'::lacZ fusions with and without the soxR -35 element (induction ratio only approximately 7-fold). SoxR thus represents a highly polar, redox-regulated transcriptional switch that maximizes the change in expression of soxS.

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Selected References

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  1. Amábile-Cuevas C. F., Demple B. Molecular characterization of the soxRS genes of Escherichia coli: two genes control a superoxide stress regulon. Nucleic Acids Res. 1991 Aug 25;19(16):4479–4484. doi: 10.1093/nar/19.16.4479. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Ansari A. Z., Bradner J. E., O'Halloran T. V. DNA-bend modulation in a repressor-to-activator switching mechanism. Nature. 1995 Mar 23;374(6520):371–375. doi: 10.1038/374370a0. [DOI] [PubMed] [Google Scholar]
  3. Casadaban M. J. Transposition and fusion of the lac genes to selected promoters in Escherichia coli using bacteriophage lambda and Mu. J Mol Biol. 1976 Jul 5;104(3):541–555. doi: 10.1016/0022-2836(76)90119-4. [DOI] [PubMed] [Google Scholar]
  4. Collado-Vides J., Magasanik B., Gralla J. D. Control site location and transcriptional regulation in Escherichia coli. Microbiol Rev. 1991 Sep;55(3):371–394. doi: 10.1128/mr.55.3.371-394.1991. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Ding H., Demple B. In vivo kinetics of a redox-regulated transcriptional switch. Proc Natl Acad Sci U S A. 1997 Aug 5;94(16):8445–8449. doi: 10.1073/pnas.94.16.8445. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Ding H., Hidalgo E., Demple B. The redox state of the [2Fe-2S] clusters in SoxR protein regulates its activity as a transcription factor. J Biol Chem. 1996 Dec 27;271(52):33173–33175. doi: 10.1074/jbc.271.52.33173. [DOI] [PubMed] [Google Scholar]
  7. Dove S. L., Joung J. K., Hochschild A. Activation of prokaryotic transcription through arbitrary protein-protein contacts. Nature. 1997 Apr 10;386(6625):627–630. doi: 10.1038/386627a0. [DOI] [PubMed] [Google Scholar]
  8. Gaudu P., Moon N., Weiss B. Regulation of the soxRS oxidative stress regulon. Reversible oxidation of the Fe-S centers of SoxR in vivo. J Biol Chem. 1997 Feb 21;272(8):5082–5086. doi: 10.1074/jbc.272.8.5082. [DOI] [PubMed] [Google Scholar]
  9. Gaudu P., Weiss B. SoxR, a [2Fe-2S] transcription factor, is active only in its oxidized form. Proc Natl Acad Sci U S A. 1996 Sep 17;93(19):10094–10098. doi: 10.1073/pnas.93.19.10094. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Greenberg J. T., Monach P., Chou J. H., Josephy P. D., Demple B. Positive control of a global antioxidant defense regulon activated by superoxide-generating agents in Escherichia coli. Proc Natl Acad Sci U S A. 1990 Aug;87(16):6181–6185. doi: 10.1073/pnas.87.16.6181. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Hidalgo E., Bollinger J. M., Jr, Bradley T. M., Walsh C. T., Demple B. Binuclear [2Fe-2S] clusters in the Escherichia coli SoxR protein and role of the metal centers in transcription. J Biol Chem. 1995 Sep 8;270(36):20908–20914. doi: 10.1074/jbc.270.36.20908. [DOI] [PubMed] [Google Scholar]
  12. Hidalgo E., Demple B. Activation of SoxR-dependent transcription in vitro by noncatalytic or NifS-mediated assembly of [2Fe-2S] clusters into apo-SoxR. J Biol Chem. 1996 Mar 29;271(13):7269–7272. doi: 10.1074/jbc.271.13.7269. [DOI] [PubMed] [Google Scholar]
  13. Hidalgo E., Demple B. An iron-sulfur center essential for transcriptional activation by the redox-sensing SoxR protein. EMBO J. 1994 Jan 1;13(1):138–146. doi: 10.1002/j.1460-2075.1994.tb06243.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Hidalgo E., Demple B. Spacing of promoter elements regulates the basal expression of the soxS gene and converts SoxR from a transcriptional activator into a repressor. EMBO J. 1997 Mar 3;16(5):1056–1065. doi: 10.1093/emboj/16.5.1056. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Hidalgo E., Ding H., Demple B. Redox signal transduction: mutations shifting [2Fe-2S] centers of the SoxR sensor-regulator to the oxidized form. Cell. 1997 Jan 10;88(1):121–129. doi: 10.1016/s0092-8674(00)81864-4. [DOI] [PubMed] [Google Scholar]
  16. Li Z., Demple B. Sequence specificity for DNA binding by Escherichia coli SoxS and Rob proteins. Mol Microbiol. 1996 Jun;20(5):937–945. doi: 10.1111/j.1365-2958.1996.tb02535.x. [DOI] [PubMed] [Google Scholar]
  17. Li Z., Demple B. SoxS, an activator of superoxide stress genes in Escherichia coli. Purification and interaction with DNA. J Biol Chem. 1994 Jul 15;269(28):18371–18377. [PubMed] [Google Scholar]
  18. Liu L. F., Wang J. C. Supercoiling of the DNA template during transcription. Proc Natl Acad Sci U S A. 1987 Oct;84(20):7024–7027. doi: 10.1073/pnas.84.20.7024. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Nunoshiba T., Demple B. Potent intracellular oxidative stress exerted by the carcinogen 4-nitroquinoline-N-oxide. Cancer Res. 1993 Jul 15;53(14):3250–3252. [PubMed] [Google Scholar]
  20. Nunoshiba T., Hidalgo E., Amábile Cuevas C. F., Demple B. Two-stage control of an oxidative stress regulon: the Escherichia coli SoxR protein triggers redox-inducible expression of the soxS regulatory gene. J Bacteriol. 1992 Oct;174(19):6054–6060. doi: 10.1128/jb.174.19.6054-6060.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Nunoshiba T., Hidalgo E., Li Z., Demple B. Negative autoregulation by the Escherichia coli SoxS protein: a dampening mechanism for the soxRS redox stress response. J Bacteriol. 1993 Nov;175(22):7492–7494. doi: 10.1128/jb.175.22.7492-7494.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Simons R. W., Houman F., Kleckner N. Improved single and multicopy lac-based cloning vectors for protein and operon fusions. Gene. 1987;53(1):85–96. doi: 10.1016/0378-1119(87)90095-3. [DOI] [PubMed] [Google Scholar]
  23. Summers A. O. Untwist and shout: a heavy metal-responsive transcriptional regulator. J Bacteriol. 1992 May;174(10):3097–3101. doi: 10.1128/jb.174.10.3097-3101.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. White D. G., Goldman J. D., Demple B., Levy S. B. Role of the acrAB locus in organic solvent tolerance mediated by expression of marA, soxS, or robA in Escherichia coli. J Bacteriol. 1997 Oct;179(19):6122–6126. doi: 10.1128/jb.179.19.6122-6126.1997. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Wu J., Dunham W. R., Weiss B. Overproduction and physical characterization of SoxR, a [2Fe-2S] protein that governs an oxidative response regulon in Escherichia coli. J Biol Chem. 1995 Apr 28;270(17):10323–10327. doi: 10.1074/jbc.270.17.10323. [DOI] [PubMed] [Google Scholar]
  26. Wu J., Weiss B. Two divergently transcribed genes, soxR and soxS, control a superoxide response regulon of Escherichia coli. J Bacteriol. 1991 May;173(9):2864–2871. doi: 10.1128/jb.173.9.2864-2871.1991. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Wu J., Weiss B. Two-stage induction of the soxRS (superoxide response) regulon of Escherichia coli. J Bacteriol. 1992 Jun;174(12):3915–3920. doi: 10.1128/jb.174.12.3915-3920.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Wurgler-Murphy S. M., Saito H. Two-component signal transducers and MAPK cascades. Trends Biochem Sci. 1997 May;22(5):172–176. doi: 10.1016/s0968-0004(97)01036-0. [DOI] [PubMed] [Google Scholar]

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