Mutagenesis by N-nitroso compounds

relationships to DNA adducts, DNA repair, and mutational efficiencies

Research output: Contribution to journalArticle

Abstract

The relationships between DNA alkylation, DNA repair and mutagenesis by N-nitroso compounds in Salmonella were examined. DNA adducts formed by treatment of the bacteria with N-nitroso compounds were monitored. Critical to the study was establishing which adducts led to mutations. Two methods were employed. In one, correlations in the dose-responses for adducts and mutagenesis were sought. For instance O6-methyl- and -ethyl-guanine, in contrast to other adducts, exhibited thresholds in their accumulation in Salmonella DNA, and mutagenesis at GC base pairs also exhibited the same threshold, suggesting a dependence of mutagenesis on the O6-alkyguanines. In the second method, mutagenesis induced by different mutagens with overlapping adduct spectra was compared. For example, EMS and ENU generate similar ratios of adenine adducts, but only ENU produces thymine adducts, and only ENU induced AT-GC and AT-CG base changes. These observations suggested that ethylthymines led to these mutations. Furthermore, it was found that these mutations were largely dependent on the presence of the plasmid, pKM101, indicating that error-prone repair activity contributes importantly in their processing to mutations. When DNA adducts by N-nitrosopyrrolidine were examined it was found that only one major adduct was detected in an excision-repair-deficient strain, and that this adduct was not present in a repair-proficient strain. Mutagenesis was also greatly reduced in the proficient strain, suggesting that mutagenesis was dependent on this adduct. From the relationships between premutagenic adducts levels adducts. This calculation assumed an average distribution of adducts and mutations and required knowledge of the target size and the types of mutations that could lead to phenotypic changes. For the unrepaired O6-methyl- and -ethyl-guanines, and the O-ethylthymines the mutational efficiencies were high (ca. 30-70%), but for the N-nitrosopyrrolidine adduct it was low (ca. 1%). Initial studies were carried out on the mutational specificities of two higher homologue N-nitroso compounds (the N-nitroso-N-propyl- and N-butyl-nitroguanidines) in uvrB/pKM101 strains. This class of nitroso compounds is known to form similar DNA adducts as ENU. Their specificities were similar to that of N-nitroso-N-ethylurea at a high dose except the fraction of mutations at AT base pairs was reduced. The fraction of GC-CG transversions was although low, increased. The mutational specificities of N-nitroso-N-methylurea and N-nitrosopyrrolidine were significantly different from the specificity of ENU as would be expected from their different adduct distributions.

Original languageEnglish (US)
Pages (from-to)177-187
Number of pages11
JournalMutation Research - Fundamental and Molecular Mechanisms of Mutagenesis
Volume233
Issue number1-2
DOIs
StatePublished - 1990

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Nitroso Compounds
DNA Adducts
Mutagenesis
DNA Repair
N-Nitrosopyrrolidine
Mutation
Guanine
Salmonella
Base Pairing
Thymine
DNA
Mutagens
Alkylation
Adenine
Plasmids
Bacteria

Keywords

  • DNA adducts, nitroso compounds
  • DNA alkylation, DNA
  • DNA repair, nitroso compounds
  • Nitroso compounds

ASJC Scopus subject areas

  • Molecular Biology
  • Health, Toxicology and Mutagenesis
  • Medicine(all)

Cite this

@article{e5e906b97b2f42c3bc47e256e458de7b,
title = "Mutagenesis by N-nitroso compounds: relationships to DNA adducts, DNA repair, and mutational efficiencies",
abstract = "The relationships between DNA alkylation, DNA repair and mutagenesis by N-nitroso compounds in Salmonella were examined. DNA adducts formed by treatment of the bacteria with N-nitroso compounds were monitored. Critical to the study was establishing which adducts led to mutations. Two methods were employed. In one, correlations in the dose-responses for adducts and mutagenesis were sought. For instance O6-methyl- and -ethyl-guanine, in contrast to other adducts, exhibited thresholds in their accumulation in Salmonella DNA, and mutagenesis at GC base pairs also exhibited the same threshold, suggesting a dependence of mutagenesis on the O6-alkyguanines. In the second method, mutagenesis induced by different mutagens with overlapping adduct spectra was compared. For example, EMS and ENU generate similar ratios of adenine adducts, but only ENU produces thymine adducts, and only ENU induced AT-GC and AT-CG base changes. These observations suggested that ethylthymines led to these mutations. Furthermore, it was found that these mutations were largely dependent on the presence of the plasmid, pKM101, indicating that error-prone repair activity contributes importantly in their processing to mutations. When DNA adducts by N-nitrosopyrrolidine were examined it was found that only one major adduct was detected in an excision-repair-deficient strain, and that this adduct was not present in a repair-proficient strain. Mutagenesis was also greatly reduced in the proficient strain, suggesting that mutagenesis was dependent on this adduct. From the relationships between premutagenic adducts levels adducts. This calculation assumed an average distribution of adducts and mutations and required knowledge of the target size and the types of mutations that could lead to phenotypic changes. For the unrepaired O6-methyl- and -ethyl-guanines, and the O-ethylthymines the mutational efficiencies were high (ca. 30-70{\%}), but for the N-nitrosopyrrolidine adduct it was low (ca. 1{\%}). Initial studies were carried out on the mutational specificities of two higher homologue N-nitroso compounds (the N-nitroso-N-propyl- and N-butyl-nitroguanidines) in uvrB/pKM101 strains. This class of nitroso compounds is known to form similar DNA adducts as ENU. Their specificities were similar to that of N-nitroso-N-ethylurea at a high dose except the fraction of mutations at AT base pairs was reduced. The fraction of GC-CG transversions was although low, increased. The mutational specificities of N-nitroso-N-methylurea and N-nitrosopyrrolidine were significantly different from the specificity of ENU as would be expected from their different adduct distributions.",
keywords = "DNA adducts, nitroso compounds, DNA alkylation, DNA, DNA repair, nitroso compounds, Nitroso compounds",
author = "Joseph Guttenplan",
year = "1990",
doi = "10.1016/0027-5107(90)90161-V",
language = "English (US)",
volume = "233",
pages = "177--187",
journal = "Mutation Research",
issn = "0027-5107",
publisher = "Elsevier",
number = "1-2",

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TY - JOUR

T1 - Mutagenesis by N-nitroso compounds

T2 - relationships to DNA adducts, DNA repair, and mutational efficiencies

AU - Guttenplan, Joseph

PY - 1990

Y1 - 1990

N2 - The relationships between DNA alkylation, DNA repair and mutagenesis by N-nitroso compounds in Salmonella were examined. DNA adducts formed by treatment of the bacteria with N-nitroso compounds were monitored. Critical to the study was establishing which adducts led to mutations. Two methods were employed. In one, correlations in the dose-responses for adducts and mutagenesis were sought. For instance O6-methyl- and -ethyl-guanine, in contrast to other adducts, exhibited thresholds in their accumulation in Salmonella DNA, and mutagenesis at GC base pairs also exhibited the same threshold, suggesting a dependence of mutagenesis on the O6-alkyguanines. In the second method, mutagenesis induced by different mutagens with overlapping adduct spectra was compared. For example, EMS and ENU generate similar ratios of adenine adducts, but only ENU produces thymine adducts, and only ENU induced AT-GC and AT-CG base changes. These observations suggested that ethylthymines led to these mutations. Furthermore, it was found that these mutations were largely dependent on the presence of the plasmid, pKM101, indicating that error-prone repair activity contributes importantly in their processing to mutations. When DNA adducts by N-nitrosopyrrolidine were examined it was found that only one major adduct was detected in an excision-repair-deficient strain, and that this adduct was not present in a repair-proficient strain. Mutagenesis was also greatly reduced in the proficient strain, suggesting that mutagenesis was dependent on this adduct. From the relationships between premutagenic adducts levels adducts. This calculation assumed an average distribution of adducts and mutations and required knowledge of the target size and the types of mutations that could lead to phenotypic changes. For the unrepaired O6-methyl- and -ethyl-guanines, and the O-ethylthymines the mutational efficiencies were high (ca. 30-70%), but for the N-nitrosopyrrolidine adduct it was low (ca. 1%). Initial studies were carried out on the mutational specificities of two higher homologue N-nitroso compounds (the N-nitroso-N-propyl- and N-butyl-nitroguanidines) in uvrB/pKM101 strains. This class of nitroso compounds is known to form similar DNA adducts as ENU. Their specificities were similar to that of N-nitroso-N-ethylurea at a high dose except the fraction of mutations at AT base pairs was reduced. The fraction of GC-CG transversions was although low, increased. The mutational specificities of N-nitroso-N-methylurea and N-nitrosopyrrolidine were significantly different from the specificity of ENU as would be expected from their different adduct distributions.

AB - The relationships between DNA alkylation, DNA repair and mutagenesis by N-nitroso compounds in Salmonella were examined. DNA adducts formed by treatment of the bacteria with N-nitroso compounds were monitored. Critical to the study was establishing which adducts led to mutations. Two methods were employed. In one, correlations in the dose-responses for adducts and mutagenesis were sought. For instance O6-methyl- and -ethyl-guanine, in contrast to other adducts, exhibited thresholds in their accumulation in Salmonella DNA, and mutagenesis at GC base pairs also exhibited the same threshold, suggesting a dependence of mutagenesis on the O6-alkyguanines. In the second method, mutagenesis induced by different mutagens with overlapping adduct spectra was compared. For example, EMS and ENU generate similar ratios of adenine adducts, but only ENU produces thymine adducts, and only ENU induced AT-GC and AT-CG base changes. These observations suggested that ethylthymines led to these mutations. Furthermore, it was found that these mutations were largely dependent on the presence of the plasmid, pKM101, indicating that error-prone repair activity contributes importantly in their processing to mutations. When DNA adducts by N-nitrosopyrrolidine were examined it was found that only one major adduct was detected in an excision-repair-deficient strain, and that this adduct was not present in a repair-proficient strain. Mutagenesis was also greatly reduced in the proficient strain, suggesting that mutagenesis was dependent on this adduct. From the relationships between premutagenic adducts levels adducts. This calculation assumed an average distribution of adducts and mutations and required knowledge of the target size and the types of mutations that could lead to phenotypic changes. For the unrepaired O6-methyl- and -ethyl-guanines, and the O-ethylthymines the mutational efficiencies were high (ca. 30-70%), but for the N-nitrosopyrrolidine adduct it was low (ca. 1%). Initial studies were carried out on the mutational specificities of two higher homologue N-nitroso compounds (the N-nitroso-N-propyl- and N-butyl-nitroguanidines) in uvrB/pKM101 strains. This class of nitroso compounds is known to form similar DNA adducts as ENU. Their specificities were similar to that of N-nitroso-N-ethylurea at a high dose except the fraction of mutations at AT base pairs was reduced. The fraction of GC-CG transversions was although low, increased. The mutational specificities of N-nitroso-N-methylurea and N-nitrosopyrrolidine were significantly different from the specificity of ENU as would be expected from their different adduct distributions.

KW - DNA adducts, nitroso compounds

KW - DNA alkylation, DNA

KW - DNA repair, nitroso compounds

KW - Nitroso compounds

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