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Journal of Bacteriology, November 2006, p. 7464-7469, Vol. 188, No. 21
0021-9193/06/$08.00+0     doi:10.1128/JB.00851-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Helicobacter pylori Genes Involved in Avoidance of Mutations Induced by 8-Oxoguanine

Aurélie Mathieu, Eyleen J. O'Rourke,^, and J. Pablo Radicella^*

Département de Radiobiologie et Radiopathologie, UMR 217 CNRS/CEA, Commissariat à l'Energie Atomique, 18 route du Panorama, F-92265 Fontenay aux Roses, France

Received 14 June 2006/ Accepted 15 August 2006

Chromosomal rearrangements and base substitutions contribute to the large intraspecies genetic diversity of Helicobacter pylori. Here we explored the base excision repair pathway for the highly mutagenic 8-oxo-7,8-dihydroguanine (8-oxoG), a ubiquitous form of oxidized guanine. In most organisms, 8-oxoG is removed by a specific DNA glycosylase (Fpg in bacteria or OGG1 in eukaryotes). In the case where replication of the lesion yields an A/8-oxoG base pair, a second DNA glycosylase (MutY) can excise the adenine and thus avoid the fixation of the mutation in the next round of replication. In a genetic screen for H. pylori genes complementing the hypermutator phenotype of an Escherichia coli fpg mutY strain, open reading frame HP0142, a putative MutY coding gene, was isolated. Besides its capacity to complement E. coli mutY strains, HP0142 expression resulted in a strong adenine DNA glycosylase activity in E. coli mutY extracts. Consistently, the purified protein also exhibited such an activity. Inactivation of HP0142 in H. pylori resulted in an increase in spontaneous mutation frequencies. An Mg-dependent AP (abasic site) endonuclease activity, potentially allowing the processing of the abasic site resulting from H. pylori MutY activity, was detected in H. pylori cell extracts. Disruption of HP1526, a putative xth homolog, confirmed that this gene is responsible for the AP endonuclease activity. The lack of evidence for an Fpg/OGG1 functional homolog is also discussed.

Published ahead of print on 25 August 2006.

These authors contributed equally to this work.

Present address: Department of Molecular Biology, Massachusetts General Hospital, and Department of Genetics, Harvard Medical School, Boston, MA 02114.

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