title: Genetic diversity of the HpyC1I restriction modification system in Helicobacter pylori.
abstract: Helicobacter pylori is unique because of the unusually high number and diversity of its restriction modification (R-M) systems. HpyC1I R-M was recently characterized and contains an endonuclease which is an isoschizomer of the endonuclease BccI. This R-M is involved in adherence to gastric epithelial cells, a crucial step in bacterial pathogenesis. This observation illustrates the fact that R-M systems have other putative biological functions in addition to protecting the bacterial genome from external DNA. The genomic diversity of HpyC1I R-M was evaluated more precisely on a large collection of H. pylori strains by PCR, susceptibility to BccI digestion and sequencing. The results obtained support the mechanism of gain and loss of this R-M system in the H. pylori genome, and suggest that it is an ancestral system which gradually disappears during H. pylori evolution, following successive steps: (1) inactivation of the endonuclease gene, followed or accompanied by: (2) inactivation of the methyltransferase genes, and then: (3) definitive loss, leaving only short endonuclease remnant sequences.
authors.affiliation: INSERM U853, 33076 Bordeaux Cedex, France. philippe.lehours@labhel.u-bordeaux2.fr
authors.forename: Philippe
authors.initials: P
authors.lastname: Lehours
authors.forename: Sandrine
authors.initials: S
authors.lastname: Dupouy
authors.forename: Julien
authors.initials: J
authors.lastname: Chaineux
authors.forename: Agnès
authors.initials: A
authors.lastname: Ruskoné-Fourmestraux
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Delchier
authors.forename: Andrea
authors.initials: A
authors.lastname: Morgner
authors.forename: Francis
authors.initials: F
authors.lastname: Mégraud
authors.forename: Armelle
authors.initials: A
authors.lastname: Ménard
mesh_terms: D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D015280:DNA Restriction-Modification Enzymes / Q000235:genetics*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D015252:Deoxyribonucleases, Type II Site-Specific / Q000235:genetics*; D023061:Gene Order; D014644:Genetic Variation; D016680:Genome, Bacterial; D016480:Helicobacter pylori / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: D015280:DNA Restriction-Modification Enzymes; D004269:DNA, Bacterial; C102950:endodeoxyribonuclease BccI; D015252:Deoxyribonucleases, Type II Site-Specific