PRIN 2007 prot. 2007LHN9JL_002 Helicobacter pylori is a microaerophilic Gram-negative bacterium that colonizes the gastric niche in over half of the human population, worldwide. It is associated with several acute and chronic stomach diseases, which develop in gastric cancers in ~ 1% of infected hosts. Disease progression depends on diverse factors, such as host dietary habits and immune-competence, as well as genetic diversity of the infecting bacterial strain. Virulent H. pylori type 1 strains, isolated from patients with severe symptoms, encompass the cag (cytotoxin associated gene) pathogenicity island (PAI), a 37 kb stretch of DNA, which codes for gene homologues of the Agrobacterium tumefaciens type IV secretion system (T4SS). In pathogenic bacteria the expression of pathogenicity island gene products has to be precisely regulated, in order to assemble a functional secretion system apparatus. The latter is required for translocation of the CagA effector molecule in H. pylori, as well as for induction of host proinflammatory cytokines, responsible in the long-term for chronic inflammations, tissue damage of the gastric epithelium and malignant cell proliferation. The effects of the cag-T4SS on host cell signalling pathways have been intensively studied in the recent past. However, virtually nothing is known about the bacterial regulatory mechanisms that underlie the co-ordinated expression of cag gene products. To begin to fill this gap we propose a comprehensive analysis of the transcriptional regulation of the cag-PAI operons. To this aim we will first identify and map bona fide cag promoters within the PAI, in order to pinpoint the complete set of cag operons. A detailed analysis of transcriptional responses of these promoters to metabolic stress signals will be performed, and integrated with transcription studies in deletion mutants of several H. pylori transcriptional regulators. To provide mechanisms for cag-PAI regulation, the role of regulator protein-DNA interactions at the cag promoters will be pursued, with special emphasis on the Ferric uptake regulator Fur, which has previously been show to extensively bind within the H. pylori cag-PAI. Finally, the as yet unexplored role of host cell-contact on cag regulation will be studied in model tissue co-cultures with gastric adenocarcinoma and/or polarized MDCK host cells-lines, using H. pylori lux reporter strains. Results will complement the structural characterization of Cag-T4SS proteins performed by the partner research unit, and shed light on fundamental aspects of T4SS regulation, assembly and function.
Alberto Danielli (2010). Regolazione trascrizionale dei geni cag codificati dalla isola di patogenicità di Helicobacter pylori.
Regolazione trascrizionale dei geni cag codificati dalla isola di patogenicità di Helicobacter pylori
DANIELLI, ALBERTO
2010
Abstract
PRIN 2007 prot. 2007LHN9JL_002 Helicobacter pylori is a microaerophilic Gram-negative bacterium that colonizes the gastric niche in over half of the human population, worldwide. It is associated with several acute and chronic stomach diseases, which develop in gastric cancers in ~ 1% of infected hosts. Disease progression depends on diverse factors, such as host dietary habits and immune-competence, as well as genetic diversity of the infecting bacterial strain. Virulent H. pylori type 1 strains, isolated from patients with severe symptoms, encompass the cag (cytotoxin associated gene) pathogenicity island (PAI), a 37 kb stretch of DNA, which codes for gene homologues of the Agrobacterium tumefaciens type IV secretion system (T4SS). In pathogenic bacteria the expression of pathogenicity island gene products has to be precisely regulated, in order to assemble a functional secretion system apparatus. The latter is required for translocation of the CagA effector molecule in H. pylori, as well as for induction of host proinflammatory cytokines, responsible in the long-term for chronic inflammations, tissue damage of the gastric epithelium and malignant cell proliferation. The effects of the cag-T4SS on host cell signalling pathways have been intensively studied in the recent past. However, virtually nothing is known about the bacterial regulatory mechanisms that underlie the co-ordinated expression of cag gene products. To begin to fill this gap we propose a comprehensive analysis of the transcriptional regulation of the cag-PAI operons. To this aim we will first identify and map bona fide cag promoters within the PAI, in order to pinpoint the complete set of cag operons. A detailed analysis of transcriptional responses of these promoters to metabolic stress signals will be performed, and integrated with transcription studies in deletion mutants of several H. pylori transcriptional regulators. To provide mechanisms for cag-PAI regulation, the role of regulator protein-DNA interactions at the cag promoters will be pursued, with special emphasis on the Ferric uptake regulator Fur, which has previously been show to extensively bind within the H. pylori cag-PAI. Finally, the as yet unexplored role of host cell-contact on cag regulation will be studied in model tissue co-cultures with gastric adenocarcinoma and/or polarized MDCK host cells-lines, using H. pylori lux reporter strains. Results will complement the structural characterization of Cag-T4SS proteins performed by the partner research unit, and shed light on fundamental aspects of T4SS regulation, assembly and function.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
