Extrachromosomal probes for mutagenesis by carcinogens: studies on the mutagenic activity of O6-methylguanine built into a unique site in a viral genome
| Autor: | Calvert L. Green, John M. Essigmann, Kerry W. Fowler, Edward L. Loechler |
|---|---|
| Rok vydání: | 1985 |
| Předmět: |
Genetics
Guanine Base Sequence DNA Repair Genes Viral O6-methylguanine Health Toxicology and Mutagenesis Public Health Environmental and Occupational Health Mutagenesis (molecular biology technique) Biology Coliphages Genome Adduct Oligodeoxyribonucleotides Extrachromosomal DNA Mutation Carcinogens Escherichia coli Carcinogen Mutagens Research Article |
| Zdroj: | Environmental Health Perspectives |
| ISSN: | 1552-9924 0091-6765 |
| DOI: | 10.1289/ehp.8562171 |
| Popis: | This work examines the mutagenic activity of O6-methylguanine (O6MeGua), a DNA adduct formed by certain carcinogenic alkylating agents. A tetranucleotide, 5'-HOTpm6GpCpA-3', was synthesized and ligated into a four-base gap in the unique Pst I site of the duplex genome of the E. coli virus, M13mp8. The double-stranded ligation product was converted to single-stranded form and used to transform E. coli to produce progeny phage. The mutation frequency of O6MeGua was defined as the percentage of progeny phage with mutations in their Pst I site, and this value was determined to be 0.4%. To determine the impact of DNA repair on mutagenesis, cellular levels of O6MeGua-DNA methyltransferase (an O6MeGua-repair protein) were depleted by treatment of host cells for virus replication with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) prior to viral DNA uptake. In these host cells, the mutation frequency due to O6MeGua increased markedly with increasing MNNG dose (the highest mutation frequency observed was 20%). DNA sequence analysis of mutant genomes revealed that in both MNNG treated and untreated cells, O6MeGua induced exclusively G to A transitions. Images FIGURE 4. |
| Databáze: | OpenAIRE |
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