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Journal of Bacteriology, February 2008, p. 926-935, Vol. 190, No. 3
0021-9193/08/$08.00+0     doi:10.1128/JB.01447-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Regulation of the yjjQ-bglJ Operon, Encoding LuxR-Type Transcription Factors, and the Divergent yjjP Gene by H-NS and LeuO ^,

Thomas Stratmann, S. Madhusudan, and Karin Schnetz^*

Institut für Genetik, Universität zu Köln, Zülpicher Str. 47, 50674 Köln, Germany

Received 7 September 2007/ Accepted 19 November 2007

The yjjQ and bglJ genes encode LuxR-type transcription factors conserved in several enterobacterial species. YjjQ is a potential virulence factor in avian pathogenic Escherichia coli. BglJ counteracts the silencing of the bgl (β-glucoside) operon by H-NS in E. coli K-12. Here we show that yjjQ and bglJ form an operon carried by E. coli K-12, whose expression is repressed by the histone-like nucleoid structuring (H-NS) protein. The LysR-type transcription factor LeuO counteracts this repression. Furthermore, the yjjP gene, encoding a membrane protein of unknown function and located upstream in divergent orientation to the yjjQ-bglJ operon, is likewise repressed by H-NS. Mapping of the promoters as well as the H-NS and LeuO binding sites within the 555-bp intergenic region revealed that H-NS binds to the center of the AT-rich regulatory region and distal to the divergent promoters. LeuO sites map to the center and to positions distal to the yjjQ promoters, while one LeuO binding site overlaps with the divergent yjjP promoter. This latter LeuO site is required for full derepression of the yjjQ promoters. The arrangement of regulatory sites suggests that LeuO restructures the nucleoprotein complex formed by H-NS. Furthermore, the data support the conclusion that LeuO, whose expression is likewise repressed by H-NS and which is a virulence factor in Salmonella enterica, is a master regulator that among other loci, also controls the yjjQ-bglJ operon and thus indirectly the presumptive targets of YjjQ and BglJ.

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* Corresponding author. Mailing address: Institut für Genetik, Universität zu Köln, Zülpicher Str. 47, 50674 Köln, Germany. Phone: 49-221-4703815. Fax: 49-221-4705185. E-mail: schnetz{at}uni-koeln.de

Published ahead of print on 30 November 2007.

Supplemental material for this article may be found at http://jb.asm.org/.

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Journal of Bacteriology, February 2008, p. 926-935, Vol. 190, No. 3
0021-9193/08/$08.00+0     doi:10.1128/JB.01447-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

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