Organization and architecture of AggR‐dependent promoters from enteroaggregative Escherichia coli

• Published in: Molecular microbiology Vol. 111; no. 2; pp. 534 - 551
• Main Authors: Yasir, Muhammad, Icke, Christopher, Abdelwahab, Radwa, Haycocks, James R., Godfrey, Rita E., Sazinas, Pavelas, Pallen, Mark J., Henderson, Ian R., Busby, Stephen J. W., Browning, Douglas F.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01-02-2019; John Wiley and Sons Inc
• Subjects: Activation; Bacteria; Binding Sites; Dependence; Diarrhea; DNA, Bacterial - genetics; DNA, Bacterial - metabolism; E coli; Epithelial cells; Escherichia coli; Escherichia coli - genetics; Escherichia coli Proteins - metabolism; Gene clusters; Gene Expression Profiling; Gene Expression Regulation, Bacterial; Gene sequencing; Pili; Promoter Regions, Genetic; Promoters; Protein Binding; Regulon; Ribonucleic acid; RNA; Sequence Analysis, RNA; Strains (organisms); Trans-Activators - metabolism; Transcription; Virulence
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/mmi.14172

Summary
Enteroaggregative Escherichia coli (EAEC), is a diarrhoeagenic human pathogen commonly isolated from patients in both developing and industrialized countries. Pathogenic EAEC strains possess many virulence determinants, which are thought to be involved in causing disease, though, the exact mechanism by which EAEC causes diarrhoea is unclear. Typical EAEC strains possess the transcriptional regulator, AggR, which controls the expression of many virulence determinants, including the attachment adherence fimbriae (AAF) that are necessary for adherence to human gut epithelial cells. Here, using RNA‐sequencing, we have investigated the AggR regulon from EAEC strain 042 and show that AggR regulates the transcription of genes on both the bacterial chromosome and the large virulence plasmid, pAA2. Due to the importance of fimbriae, we focused on the two AAF/II fimbrial gene clusters in EAEC 042 (afaB‐aafCB and aafDA) and identified the promoter elements and AggR‐binding sites required for fimbrial expression. In addition, we examined the organization of the fimbrial operon promoters from other important EAEC strains to understand the rules of AggR‐dependent activation. Finally, we generated a series of semi‐synthetic promoters to define the minimal sequence required for AggR‐mediated activation and show that the correct positioning of a single AggR‐binding site is sufficient to confer AggR‐dependence.
Enteroaggregative Escherichia coli (EAEC) is a commonly isolated human pathogen that causes mucoid diarrhoea. As EAEC virulence is controlled by the AggR master transcription factor, we use RNA‐sequencing to identify the AggR‐regulated genes in the pathogenic EAEC strain 042. We report the structure of several AggR‐dependent promoters in order to understand the mechanism of AggR‐mediated transcription activation.