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J. Bacteriol., 11 1997, 6807-6815, Vol 179, No. 21
Q Xu, RM Peek Jr, GG Miller and MJ Blaser
To understand mechanisms of DNA methylation in Helicobacter pylori, a human
pathogen associated with peptic ulcer disease and gastric adenocarcinoma,
we cloned a putative DNA methyltransferase gene, hpyIM. This gene contains
a 990-bp open reading frame encoding a 329-amino- acid protein, M.HpyI.
Sequence analysis revealed that M.HpyI was closely related to
CATG-recognizing adenine DNA methyltransferases, including M.NlaIII in N.
lactamica. hpyIM was present in all H. pylori strains tested. DNA from
wild-type H. pylori strains was resistant to digestion by SphI and NlaIII,
which recognize DNA at sites containing CATG, whereas their isogenic hpyIM
mutants were susceptible, indicating lack of modification. Overexpression
of hpyIM in Escherichia coli rendered DNA from these cells resistant to
NlaIII digestion, confirming the role of hpyIM in modifying CATG sites. We
conclude that hpyIM encodes a DNA methyltransferase, M.HpyI, that is well
conserved among diverse H. pylori strains and that modifies H. pylori
genomes at CATG sites.
Copyright © 1997, American Society for Microbiology
The Helicobacter pylori genome is modified at CATG by the product of hpyIM
Department of Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
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