Genetic diversity of the HpyC1I restriction modification system in Helicobacter pylori.
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.
Lehours
Philippe
P
INSERM U853, 33076 Bordeaux Cedex, France. philippe.lehours@labhel.u-bordeaux2.fr
Dupouy
Sandrine
S
Chaineux
Julien
J
Ruskoné-Fourmestraux
Agnès
A
Delchier
Jean-Charles
JC
Morgner
Andrea
A
Mégraud
Francis
F
Ménard
Armelle
A
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
D015280:DNA Restriction-Modification Enzymes; D004269:DNA, Bacterial; C102950:endodeoxyribonuclease BccI; D015252:Deoxyribonucleases, Type II Site-Specific