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Base modifications in plasmid DNA caused by potassium permanganate
S A Akman1, J H Doroshow, M Dizdaroglu
1Department of Medical Oncology, City of Hope National Medical Center, Duarte, California 91010.
Archives of Biochemistry and Biophysics
|October 1, 1990
Summary
Potassium permanganate (KMnO4) modifies DNA bases, including thymine, cytosine, guanine, and adenine, even under mild conditions. These findings impact previous research on DNA modification and mutagenicity.
Area of Science:
- Molecular Biology
- Biochemistry
- Chemical Biology
Background:
- Potassium permanganate (KMnO4) is a known oxidizing agent used to modify DNA bases.
- Previous research indicated preferential modification of thymine (Thy) by mild KMnO4, with cytosine (Cyt) and guanine (Gua) modification only occurring under harsher conditions.
Purpose of the Study:
- To investigate the effects of varying KMnO4 concentrations on DNA base modification.
- To identify novel KMnO4-induced modification products in plasmid DNA.
Main Methods:
- Denatured plasmid DNA was treated with KMnO4 (0.015-1.5 mM) at 4°C.
- DNA was hydrolyzed, trimethylsilylated, and analyzed using gas chromatography-mass spectrometry/selected ion monitoring.
Main Results:
- KMnO4 treatment induced a concentration-dependent increase in modified products for Thy, Cyt, Ade, and Gua bases.
- Novel modification products for Cyt, Gua, and Ade were identified, including Cyt glycol, 5,6-dihydroxycytosine, 5-hydroxyhydantoin, 8-hydroxyadenine, and 8-hydroxyguanine.
- Minimal increases in specific Ade and Gua products were observed at higher KMnO4 concentrations (≥0.8 mM).
Conclusions:
- KMnO4 modifies all four DNA bases (Thy, Cyt, Gua, Ade) even under mild conditions.
- This study provides the first identification of Cyt, Gua, and Ade modification products induced by KMnO4.
- Previous studies using KMnO4 as a Thy-specific probe or to study Thy glycol mutagenicity require re-evaluation due to non-specific base modification.