title: Restriction-modification systems may be associated with Helicobacter pylori virulence.
abstract: Restriction-modification (R-M) systems are exclusive to unicellular organisms and ubiquitous in the bacterial world. Bacteria use R-M systems as a defense against invasion by foreign DNA. Analysis of the genome sequences of Helicobacter pylori strains 26 695 and J99 identified an extraordinary number of genes with homology to R-M genes in other bacterial species. All H. pylori strains possess their own unique complement of active R-M systems. All of the methylases that have been studied so far were present in all major human population groupings, suggesting that their horizontal acquisition pre-dated the separation of these populations. The two most strongly conserved methylase genes of H. pylori, hpy IM and hpy IIIM, are both preceded by alternative genes that compete for presence at their loci, and furthermore these genes may be associated with H. pylori pathogenicity. Further study should investigate the roles of H. pylori R-M systems.
authors.affiliation: Department of Gastroenterology, Nagoya University Graduate School of Medicine, Nagoya, Japan. takafumiando-gi@umin.ac.jp
authors.forename: Takafumi
authors.initials: T
authors.lastname: Ando
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Ishiguro
authors.forename: Osamu
authors.initials: O
authors.lastname: Watanabe
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Miyake
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Kato
authors.forename: Satoshi
authors.initials: S
authors.lastname: Hibi
authors.forename: Shunya
authors.initials: S
authors.lastname: Mimura
authors.forename: Masanao
authors.initials: M
authors.lastname: Nakamura
authors.forename: Ryoji
authors.initials: R
authors.lastname: Miyahara
authors.forename: Naoki
authors.initials: N
authors.lastname: Ohmiya
authors.forename: Yasumasa
authors.initials: Y
authors.lastname: Niwa
authors.forename: Hidemi
authors.initials: H
authors.lastname: Goto
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D015280:DNA Restriction-Modification Enzymes / Q000235:genetics* / Q000378:metabolism; D019143:Evolution, Molecular; D016481:Helicobacter Infections / Q000453:epidemiology / Q000382:microbiology*; D016480:Helicobacter pylori / Q000201:enzymology / Q000235:genetics* / Q000472:pathogenicity*; D006801:Humans; D012111:Residence Characteristics; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific) / Q000235:genetics; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D015280:DNA Restriction-Modification Enzymes; C108842:DNA modification methylase HpyI; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific)