Suppression of spontaneous and hydrogen peroxide-induced mutations by a MutT-type nucleotide pool sanitization enzyme, the Escherichia coli Orf135 protein

Background: We recently found that the Escherichia coli Orf135 protein, a MutT-type enzyme, hydrolysed 2-hydroxy-dATP (2-OH-dATP), and less efficiently, 8-hydroxy-dGTP. Results: In this study, we examined the effects of the absence of the orf135 gene. Frequencies of spontaneous and H2O2-induced mutations were two- to three-fold higher in the orf135(-) strain than in the wild-type strain. These mutations include various mutations involving a G:C-->T:A transversion, the same type of mutation elicited by 2-OH-dATP. Over-expression of the Orf135 protein suppressed mutations even in the wild-type strain, as well as in the orf135(-) strain. Conclusions: The mutator phenotype of bacteria lacking the Orf135 protein suggests that this protein is involved in the suppression of mutations induced by oxidized deoxynucleotides in vivo and that various MutT-type enzymes contribute to nucleotide pool sanitization.