PMID:1986273
| Citation |
Takano, K, Nakamura, T and Sekiguchi, M (1991) Roles of two types of O6-methylguanine-DNA methyltransferases in DNA repair. Mutat. Res. 254:37-44 |
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| Abstract |
Escherichia coli possesses 2 types of O6-methylguanine-DNA methyltransferases, one inducible and the other constitutive. These enzymes are coded by the ada and the ogt genes, respectively. Using a synthetic ogt-specific probe, we mapped ogt at 29.4 min, near the 5'-flanking region of the nirR gene, on the E. coli chromosome. To elucidate the roles of the 2 types of methyltransferases in DNA repair, we constructed mutant strains which lack either one or both of the genes. In either the ada+ or the ada- background, the ogt mutation had no effect on cell survival after N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) treatment. On the other hand, ada- ogt- cells were more prone to mutation as compared to the ada- ogt+ cells exposed to MNNG. The frequency of spontaneous mutation of cells defective in either one or both of the genes was the same, however, the introduction of the ogt+ plasmid into the cells produced a 2-3-fold decrease in the frequency of spontaneous mutation. O6-Methylguanine-DNA methyltransferases appear to eliminate premutagenic DNA lesions not only from cells exposed to alkylating agents but also from those grown in the absence of the agents. |
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| Keywords |
Base Sequence; Blotting, Southern; Chromosome Mapping; Chromosomes, Bacterial; Cloning, Molecular; DNA Repair; Escherichia coli/enzymology; Escherichia coli/genetics; Escherichia coli/growth & development; Genes, Bacterial; Methylnitronitrosoguanidine/pharmacology; Methyltransferases/metabolism; Molecular Sequence Data; Mutation; O(6)-Methylguanine-DNA Methyltransferase; Oligonucleotide Probes; Plasmids; Restriction Mapping |
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