uvrA and recA Mutations Inhibit a Site-Specific Transition Produced by a Single O6-methylguanine in Gene G of Bacteriophage φ X174
Abstract
Using site-specific mutagenesis, we have examined the mutagenic activity in vivo of O6-methylguanine or O6-n-butylguanine located at a preselected site in gene G of bacteriophage phi X174. The experiments were designed so that the phage mutant produced by a targeted transition from either of these alkylated derivatives would be recognizable by a simple plaque assay. Spheroplasts derived from normal and repair-deficient cells were transfected, and the lysates were screened for mutant virus. In cells with normal repair, DNA carrying the methylguanine produced the expected transition in 15% of the total phage; DNA carrying the butylguanine produced the same mutation in 0.3% of the phage. In cells deficient in excision repair (uvrA) the transition frequency went up by a factor of 8 for O6-butylguanine and down by a factor of 40 for O6-methylguanine. In cells deficient in recombination (recA), the transition frequency increased 1.5-fold for butylguanine and decreased by a factor of 8 for methylguanine. The data show that both methyl- and butylguanine produce site-directed transitions in phi X174; the transition occurs in recA cells; the frequency of the transition is influenced by both recA and uvrA mutations; the recA and uvrA mutations alter the transition frequency for methylguanine and butylguanine in opposite directions.
- Publication:
-
Proceedings of the National Academy of Science
- Pub Date:
- November 1985
- DOI:
- 10.1073/pnas.82.21.7173
- Bibcode:
- 1985PNAS...82.7173C