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Journal of Bacteriology, September 2002, p. 4800-4810, Vol. 184, No. 17
0021-9193/02/$04.00+0     DOI: 10.1128/JB.184.17.4800-4810.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Growth Phase-Dependent Regulation of Target Gene Promoters for Binding of the Essential Orphan Response Regulator HP1043 of Helicobacter pylori

Isabel Delany,1 Gunther Spohn,1,{dagger} Rino Rappuoli,1 and Vincenzo Scarlato1,2*

Department of Molecular Biology, IRIS, Chiron SpA, 53100 Siena,1 Department of Biology, University of Bologna, 40126 Bologna, Italy2

Received 19 April 2002/ Accepted 4 June 2002

Helicobacter pylori encodes three two-component systems and two orphan response regulators (RRs) that are predicted to be involved in transcriptional regulation. The HP1043 gene encodes an essential OmpR-like RR, 1043RR, for which no histidine kinase has been identified. Gel filtration and cross-linking experiments on the purified 1043RR protein reveals that this protein is a dimer and in vivo dimerization assays localize the dimerization to the N-terminal regulatory domain. DNA-binding studies have revealed two targets for specific binding of the 1043RR protein and moreover, phosphorylation of the protein was not needed for the activation of binding. Footprinting analysis demonstrated that the 1043RR protein binds to its own promoter, P1043, overlapping the -35 promoter element from positions -17 to -45, suggesting that this protein is autoregulatory. In addition, it binds at a similar location, spanning nucleotides from positions -22 to -51 at the promoter of the methyl-accepting chemotaxis tlpB gene, PtlpB. A possible inverted repeat was identified in the binding sites of both promoters. In an attempt to overexpress 1043RR in H. pylori, the 10-fold induction in transcription of a second copy of HP1043 with use of an inducible promoter failed to increase cellular levels of the RR protein, suggesting that 1043RR is tightly regulated at a posttranscriptional level. The P1043 and PtlpB promoters were demonstrated to be coordinately regulated in response to growth phase in H. pylori. The essential role of HP1043 in encoding a cell cycle regulator is discussed.

* Corresponding author. Mailing address: Department of Molecular Biology, IRIS, Chiron SpA, Via Fiorentina 1, 53100 Siena, Italy. Phone: 39-0577-243565. Fax: 39-0577-243564. E-mail: enzo_scarlato{at}chiron.it.

{dagger} Present address: Department of Vaccines, Cytos Biotechnology AG, Zurich-Schlieren, Switzerland.

Journal of Bacteriology, September 2002, p. 4800-4810, Vol. 184, No. 17
0021-9193/02/$04.00+0     DOI: 10.1128/JB.184.17.4800-4810.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



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