Ler, a Versatile Global Regulator from E. Coli O157 and Related Strains

This proposal draws on the expertise of three applicants with an international reputation (all three with PNAS papers in the last year) to address important questions within the AF theme 'Control of Food-borne Pathogens'. <P>

Enterohaemorrhagic strains of E. coli (EHEC), especially E. coli O157:H7, present a formidable challenge to the Agri- Food industry. Virulence in EHEC relies on a type III secretion system, encoded by the locus for enterocyte effacement (the LEE) to mediate translocation of effector proteins from the bacterial cytoplasm into the cytoplasm of eukaryotic cells. The LEE-encoded regulator, Ler, plays a pivotal role in the regulation of gene expression within the LEE. Ler is homologous to the intensively studied global regulator, H-NS. <P>Building on this homology and on our own preliminary work, we now wish to address a number of important research questions concerning Ler: <OL> <LI> Is Ler, like H-NS, a global regulator binding to multiple sites throughout the genome? We have preliminary transcriptomics data to suggest that Ler influences many genes outside the LEE, plus we have unique local expertise in transcriptomics and chromatin immunoprecipitation to perform timely studies that define the global effects of Ler in different settings and distinguish direct from indirect influences. <LI>Does Ler engage in dimerisation and homo- and hetero- oligomerisation, and how might these activities relate to its function? With local expertise in appropriate techniques and input from a leading expert on H-NS (Ladbury), we are well placed to address this question.<LI>Do protein- protein interaction networks converging on Ler provide a route for coupling protein secretion to transcriptional regulation? We will explore the protein-protein interaction networks that converge on Ler and explore the hypothesis that these pathways provide a route for coupling protein secretion to transcriptional regulation.