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Mol Microbiol. 2010 Jun 1;76(5):1306-21. doi: 10.1111/j.1365-2958.2010.07174.x. Epub 2010 Apr 27.

The LysR-type regulator QseA regulates both characterized and putative virulence genes in enterohaemorrhagic Escherichia coli O157:H7.

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University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd., Dallas, TX 75390-9048, USA.


Enterohaemorrhagic Escherichia coli (EHEC) colonizes the large intestine, causing attaching and effacing (AE) lesions. Most of the genes involved in AE lesion formation are encoded within a chromosomal pathogenicity island termed the locus of enterocyte effacement (LEE). The LysR-type transcriptional factor QseA regulates the LEE by binding to the regulatory region of ler. We performed transcriptome analyses comparing wild-type (WT) EHEC and the qseA mutant to elucidate QseA's role in gene regulation. During both growth phases, several genes carried in O-islands were activated by QseA, whereas genes involved in cell metabolism were repressed. During late-logarithmic growth, QseA activated expression of the LEE genes as well as non-LEE-encoded effector proteins. We also performed electrophoretic mobility shift assays, competition experiments and DNase I footprints. The results demonstrated that QseA directly binds both the ler proximal and distal promoters, its own promoter, as well as promoters of genes encoded in EHEC-specific O-islands. Additionally, we mapped the transcriptional start site of qseA, leading to the identification of two promoter sequences. Taken together, these results indicate that QseA acts as a global regulator in EHEC, co-ordinating expression of virulence genes.

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