Stereochemistry of the in vitro and in vivo methylation of DNA by (R)- and (S)-N-[2H1,3H]methyl-N-nitrosourea and (R)- and (S)-N-nitroso-N- [2H1,3H]methyl-N-methylamine

Thomas Spratt, Thomas M. Zydowsky, Heinz G. Floss

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Reaction of DNA with the carcinogens N-methyl-N-nitrosourea and N- nitroso-N,N-dimethylamine produces several methylated species including the premutagenic O6-methylguanine. The mechanism of methylation is believed to be through a methanediazonium ion. We have studied the mechanism of methylation of DNA by these carcinogens by analyzing the stereochemistry of the methyl transfer. DNA was methylated in vitro by (R)- and (S)-N- [2H1,3H]methyl-N-nitrosourea and in vivo by (R)- and (S)-N- [2H1,3H]methyl-N-methyl-N-nitrosamine and (R)-and (S)-N- [2H1,3H]methyl-N-nitrosourea. 7-Methylguanine, 3-methyladenine, O6- methylguanine, and the methylated phosphate backbone were isolated. The methyl groups were converted into acetic acid, and the stereochemistry was analyzed. The identity of the nucleophile did not influence the stereochemistry of the methylation reaction. It was found that the methyl group was transferred with an average of 73% inversion and 27% retention of configuration. The most likely mechanism for the retention of configuration is through multiple methylation events in which nucleophiles which initially react with the methanediazonium ion react as electrophiles with DNA.

Original languageEnglish (US)
Pages (from-to)1412-1419
Number of pages8
JournalChemical research in toxicology
Volume10
Issue number12
DOIs
StatePublished - Dec 1 1997

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Stereochemistry
Methylation
DNA Methylation
Carcinogens
Nucleophiles
DNA
Ions
Methylnitrosourea
Nitrosamines
Acetic Acid
Phosphates
methylamine
In Vitro Techniques
O-(6)-methylguanine

All Science Journal Classification (ASJC) codes

  • Toxicology

Cite this

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title = "Stereochemistry of the in vitro and in vivo methylation of DNA by (R)- and (S)-N-[2H1,3H]methyl-N-nitrosourea and (R)- and (S)-N-nitroso-N- [2H1,3H]methyl-N-methylamine",
abstract = "Reaction of DNA with the carcinogens N-methyl-N-nitrosourea and N- nitroso-N,N-dimethylamine produces several methylated species including the premutagenic O6-methylguanine. The mechanism of methylation is believed to be through a methanediazonium ion. We have studied the mechanism of methylation of DNA by these carcinogens by analyzing the stereochemistry of the methyl transfer. DNA was methylated in vitro by (R)- and (S)-N- [2H1,3H]methyl-N-nitrosourea and in vivo by (R)- and (S)-N- [2H1,3H]methyl-N-methyl-N-nitrosamine and (R)-and (S)-N- [2H1,3H]methyl-N-nitrosourea. 7-Methylguanine, 3-methyladenine, O6- methylguanine, and the methylated phosphate backbone were isolated. The methyl groups were converted into acetic acid, and the stereochemistry was analyzed. The identity of the nucleophile did not influence the stereochemistry of the methylation reaction. It was found that the methyl group was transferred with an average of 73{\%} inversion and 27{\%} retention of configuration. The most likely mechanism for the retention of configuration is through multiple methylation events in which nucleophiles which initially react with the methanediazonium ion react as electrophiles with DNA.",
author = "Thomas Spratt and Zydowsky, {Thomas M.} and Floss, {Heinz G.}",
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T1 - Stereochemistry of the in vitro and in vivo methylation of DNA by (R)- and (S)-N-[2H1,3H]methyl-N-nitrosourea and (R)- and (S)-N-nitroso-N- [2H1,3H]methyl-N-methylamine

AU - Spratt, Thomas

AU - Zydowsky, Thomas M.

AU - Floss, Heinz G.

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N2 - Reaction of DNA with the carcinogens N-methyl-N-nitrosourea and N- nitroso-N,N-dimethylamine produces several methylated species including the premutagenic O6-methylguanine. The mechanism of methylation is believed to be through a methanediazonium ion. We have studied the mechanism of methylation of DNA by these carcinogens by analyzing the stereochemistry of the methyl transfer. DNA was methylated in vitro by (R)- and (S)-N- [2H1,3H]methyl-N-nitrosourea and in vivo by (R)- and (S)-N- [2H1,3H]methyl-N-methyl-N-nitrosamine and (R)-and (S)-N- [2H1,3H]methyl-N-nitrosourea. 7-Methylguanine, 3-methyladenine, O6- methylguanine, and the methylated phosphate backbone were isolated. The methyl groups were converted into acetic acid, and the stereochemistry was analyzed. The identity of the nucleophile did not influence the stereochemistry of the methylation reaction. It was found that the methyl group was transferred with an average of 73% inversion and 27% retention of configuration. The most likely mechanism for the retention of configuration is through multiple methylation events in which nucleophiles which initially react with the methanediazonium ion react as electrophiles with DNA.

AB - Reaction of DNA with the carcinogens N-methyl-N-nitrosourea and N- nitroso-N,N-dimethylamine produces several methylated species including the premutagenic O6-methylguanine. The mechanism of methylation is believed to be through a methanediazonium ion. We have studied the mechanism of methylation of DNA by these carcinogens by analyzing the stereochemistry of the methyl transfer. DNA was methylated in vitro by (R)- and (S)-N- [2H1,3H]methyl-N-nitrosourea and in vivo by (R)- and (S)-N- [2H1,3H]methyl-N-methyl-N-nitrosamine and (R)-and (S)-N- [2H1,3H]methyl-N-nitrosourea. 7-Methylguanine, 3-methyladenine, O6- methylguanine, and the methylated phosphate backbone were isolated. The methyl groups were converted into acetic acid, and the stereochemistry was analyzed. The identity of the nucleophile did not influence the stereochemistry of the methylation reaction. It was found that the methyl group was transferred with an average of 73% inversion and 27% retention of configuration. The most likely mechanism for the retention of configuration is through multiple methylation events in which nucleophiles which initially react with the methanediazonium ion react as electrophiles with DNA.

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