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

Mutagenesis. 1997 Jan;12(1):23-8. doi: 10.1093/mutage/12.1.23.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / drug effects
  • Adenosine Triphosphatases / genetics
  • Bacterial Proteins / drug effects
  • Bacterial Proteins / genetics
  • Cell Death / drug effects
  • Cell Death / genetics
  • DNA Glycosylases*
  • DNA Repair / drug effects*
  • DNA-Binding Proteins / drug effects
  • DNA-Binding Proteins / genetics
  • Drug Resistance, Microbial / genetics
  • Escherichia coli / drug effects
  • Escherichia coli / genetics*
  • Escherichia coli Proteins*
  • Mutagenesis / drug effects*
  • Mutation
  • N-Glycosyl Hydrolases / drug effects
  • N-Glycosyl Hydrolases / genetics*
  • Nitrous Acid / pharmacology*
  • Recombinant Proteins / genetics
  • beta-Galactosidase / drug effects
  • beta-Galactosidase / genetics


  • Bacterial Proteins
  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • Recombinant Proteins
  • beta-Galactosidase
  • DNA Glycosylases
  • N-Glycosyl Hydrolases
  • DNA-3-methyladenine glycosidase II
  • UvrA protein, E coli
  • Adenosine Triphosphatases
  • Nitrous Acid