This Article Full Text (PDF) Other Versions of this Article: JB.00108-07v1 189/24/8914    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Skoglund, A. Articles by Engstrand, L. Search for Related Content PubMed PubMed Citation Articles by Skoglund, A. Articles by Engstrand, L.

 Previous Article  |  Next Article 

J. Bacteriol. doi:10.1128/JB.00108-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Functional analysis of the M.HpyAIV DNA-methyltransferase of Helicobacter pylori

Department of Microbiology, Cell and Tumor Biology, Karolinska Institutet, 171 77, Stockholm, Sweden; Swedish Institute for Infectious Disease Control, 171 82, Solna, Sweden; EMBL Hamburg Outstation, Notkestrasse 85, 22303 Hamburg, Germany; Biology Education Center, Uppsala University, Box 592, 751 24 Uppsala, Sweden

^* To whom correspondence should be addressed. Email: Lars.Engstrand{at}smi.ki.se.

	Abstract

A large number of genes encoding restriction- modification (R-M) systems are found in the human pathogen Helicobacter pylori genome. R-M genes comprise approximately ten percent of the strain-specific genes, but the relevance for having such an abundance of these genes is not clear. The type II methyltransferase (MTase), M.HpyAIV, which recognizes GANTC sites, was present in 60% of the H. pylori strains analyzed, whereof 69% were resistant to restriction enzyme digestion, which indicated the presence of an active MTase. H. pylori strains with an inactive M.HpyAIV phenotype contained deletions in regions of homopolymers within the gene, which resulted in premature translational stops, suggesting that M.HpyAIV may be subjected to phase variation by slipped-strand mechanism. A hpyAIVM mutant was constructed by insertional mutagenesis and this mutant showed the same viability and ability to induce interleukin-8 in epithelial cells as the wildtype in vitro, but had as expected lost the ability to protect its self-DNA from digestion by a cognate restriction enzyme. The M.HpyAIV from H. pylori strain 26695 was over-expressed in Escherichia coli, and the protein was purified and was able to bind to DNA and protect GANTC sites from digestion in vitro. A bioinformatic analysis of the number of GANTC sites located in predicted regulatory regions of H. pylori strains 26695 and J99 resulted in a number of candidate genes. katA, a selected candidate gene, was further analyzed by quantitative real-time RT-PCR and shown to be significantly down-regulated in the hpyAIVM mutant compared to the wildtype strain. This demonstrates the influence of M.HpyAIV methylation in gene expression.