Organization of the LEE1 operon regulatory region of enterohaemorrhagic Escherichia coli O157:H7 and activation by GrlA

• Published in: Molecular microbiology 2011-01, Vol.79 (2), p.468-483
• Main Authors: Islam, Md. Shahidul, Bingle, Lewis E.H, Pallen, Mark J, Busby, Stephen J.W
• Format: Article
• Language: English
• Subjects: Base Sequence; Cells; DNA Mutational Analysis; DNA, Bacterial - genetics; E coli; Escherichia coli; Escherichia coli O157 - genetics; Escherichia coli Proteins - biosynthesis; Escherichia coli Proteins - metabolism; Gene expression; Gene Expression Regulation, Bacterial; Genetic Loci; Microbiology; Models, Biological; Molecular Sequence Data; Mutation; Operon; Phosphoproteins - biosynthesis; Plasmids; Promoter Regions, Genetic; Trans-Activators - metabolism; Transcription, Genetic
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/j.1365-2958.2010.07460.x

Expression of the genes in the locus of enterocyte effacement (LEE) in enterohaemorrhagic Escherichia coli is primarily co-ordinated by expression of the LEE1 operon. GrlA is a LEE-encoded transcription regulator that has been proposed to be involved in the regulation of expression of the LEE1 operon. We describe a simple plasmid-based system to investigate the LEE1 operon regulatory region and to study GrlA-dependent effects. We report that GrlA can activate transcription initiation at the LEE1 P1 promoter by binding to a target located within the 18-base-pair spacer between the promoter −10 and −35 elements, which were defined by mutational analysis. Shortening this spacer to 17 base pairs increases P1 promoter activity and short-circuits GrlA-dependent activation. Hence, at the P1 promoter, the action of GrlA resembles that of many MerR family transcription activators at their target promoters.