The LysR-type regulator QseA regulates both characterized and putative virulence genes in enterohaemorrhagic Escherichia coli O157:H7.
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.
Kendall
Melissa M
MM
University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd., Dallas, TX 75390-9048, USA.
Rasko
David A
DA
Sperandio
Vanessa
V
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D019453:Escherichia coli O157 / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D046228:Microarray Analysis; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C457339:QseA protein, E coli; D015534:Trans-Activators; D014157:Transcription Factors; C073470:LysR protein, Bacteria