title: uvrA and recA mutations inhibit a site-specific transition produced by a single O6-methylguanine in gene G of bacteriophage phi 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.
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D010584:Bacteriophage phi X 174 / Q000235:genetics*; D003062:Codon; D004260:DNA Repair; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics*; D005814:Genes, Viral; D006147:Guanine / Q000031:analogs & derivatives* / Q000378:metabolism; D009154:Mutation; D011938:Rec A Recombinases / Q000235:genetics / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D003062:Codon; D004279:DNA, Viral; D006147:Guanine; C046953:O(6)-n-butylguanine; C008449:O-(6)-methylguanine; D011938:Rec A Recombinases