Transcription of the uropathogenic Escherichia coli vat gene is driven by multiple promoters whose activity is modulated by the cyclic AMP receptor protein

Uropathogenic Escherichia coli (UPEC), a cause of urinary tract infections, expresses various virulence factors to enable it to infect and persist, overcoming host defences. One of these is the vacuolating autotransporter toxin (Vat), which causes vacuole formation and cellular damage in bladder epithelial cells. Bacteria tightly regulate transcript initiation of most virulence factor genes using either bespoke transcription factors, or, sometimes, global transcription factors, such as the cyclic AMP receptor protein (CRP), which regulates hundreds of bacterial genes, typically responding to nutritional stress. We report that CRP binds to the regulatory region of the vat gene and describe the complex nature of regulation of vat gene transcription in UPEC CFT073. In vivo and in vitro analysis revealed that whilst the vat regulatory region contains a CRP-activated promoter, P1, two additional promoters, P2 and P3, ensure that net promoter activity is not dependent on CRP. Functional -10 and -35 elements were identified for the P2 promoter, which is suppressed by CRP binding, blocking the -35 element. Expression from the P3 promoter is also supressed by binding of CRP over the transcript start site.