Effects of nitrous acid treatment on the survival and mutagenesis of Escherichia coli cells lacking base excision repair (hypoxanthine-DNA glycosylase-ALK A protein) and/or nucleotide excision repair.
Deoxyinosine occurs in DNA by spontaneous deamination of adenine or by incorporation of dITP during replication. Hypoxanthine residues (HX) are mutagenic and give rise to A-T-->G-C transition. They are substrates for the Escherichia coli product of the alkA gene, the 3-methyl-adenine-DNA glycosylase II (ALK A protein). In mammalian cells and in yeast, HX is excised by the counterpart of ALK A protein, the ANPG or the MAG proteins respectively. We have investigated in vivo the contribution of the alkA gene to counteract the lethal and/or mutagenic effects of HX residues induced by nitrous acid treatment. Using an E.coli strain allowing the detection of A-T-->G-C transition, we show that the alkA mutant has a slightly increased spontaneous rate of mutation and about the same sensitivity when treated with HNO2 as compared with the wild-type strain. Using the E.coli alkA mutant carrying a multicopy plasmid expressing the ALK A protein or the ANPG protein, we barely observe any effect of HNO2 treatment on sensitivity and mutation rate of the bacteria. In contrast, the same experiment performed with a uvrA- strain, deficient in nucleotide excision repair (NER), shows that this mutant is extremely sensitive to HNO2 treatment. Furthermore, the sensitivity and the spontaneous mutation rate observed in the double mutant alkA- uvrA- are almost identical to those of the uvrA- mutant. Hence, NER has the major role in vivo for the repair of lethal and mutagenic lesions induced by HNO2.
Sidorkina
O
O
Groupe Réparation des Lésions Radio- et Chimio-Induites, URA 147 CNRS. Institut Gustave Roussy, Villejuif, France.
Saparbaev
M
M
Laval
J
J
D000251:Adenosine Triphosphatases / Q000187:drug effects / Q000235:genetics; D001426:Bacterial Proteins / Q000187:drug effects / Q000235:genetics; D016923:Cell Death / Q000187:drug effects / Q000235:genetics; D045647:DNA Glycosylases; D004260:DNA Repair / Q000187:drug effects*; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000235:genetics; D004352:Drug Resistance, Microbial / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D029968:Escherichia coli Proteins; D016296:Mutagenesis / Q000187:drug effects*; D009154:Mutation; D009699:N-Glycosyl Hydrolases / Q000187:drug effects / Q000235:genetics*; D009608:Nitrous Acid / Q000494:pharmacology*; D011994:Recombinant Proteins / Q000235:genetics; D001616:beta-Galactosidase / Q000187:drug effects / Q000235:genetics
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D011994:Recombinant Proteins; D001616:beta-Galactosidase; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C076131:DNA-3-methyladenine glycosidase II; C068631:UvrA protein, E coli; D000251:Adenosine Triphosphatases; D009608:Nitrous Acid