Antimutagenic specificities of two plant glycosylases, oxoguanine glycosylase and formamidopyrimidine glycosylase, assayed in vivo.

The base-excision repair process protects genomes by removing and replacing altered bases in DNA. Two analogous glycosylases, oxoguanine glycosylase (OGG) and formamidopyrimidine glycosylase (FPG), can start the process by removing oxidized guanine, the most common modification that leads to misreading of DNA. Plants possess genes for both types of glycosylases. We have tested the hypothesis that the two enzymes in plants have diverged in their specificities by inserting the genes for each enzyme from Arabidopsis thaliana L. into Escherichia coli strains designed to indicate the frequencies of the six possible single-base changes. Both enzymes retain the ability to reduce the rate of GC-->TA transversion mutations. Both enzymes also reduce the frequency of two other base-change mutations, GC-->AT and AT-->TA. We do not find a divergence in the repair capabilities of the two enzymes, as measured in E. coli, although surprisingly FPG appears to increase the rate of mutations in one particular strain.