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DNA strand scission by benzo[a]pyrene diol epoxides
Science (New York, N.Y.)
|August 12, 1977
Summary
Benzo[a]pyrene diol epoxides cause DNA strand breaks in a concentration-dependent manner. This DNA nicking results from the formation and hydrolysis of unstable phosphotriesters, a minor modification pathway.
Area of Science:
- Environmental Toxicology
- Molecular Biology
- Biochemistry
Background:
- Polycyclic aromatic hydrocarbons (PAHs) like benzo[a]pyrene are environmental mutagens.
- Benzo[a]pyrene diol epoxides (BPDEs) are reactive metabolites implicated in DNA damage and carcinogenesis.
- Understanding the precise mechanisms of BPDE-induced DNA modification is crucial for risk assessment.
Purpose of the Study:
- To investigate the ability of syn- and anti-benzo[a]pyrene diol epoxides to induce DNA strand breaks.
- To quantify the extent of DNA nicking relative to overall DNA modification by BPDEs.
- To elucidate the mechanistic pathway leading to BPDE-induced DNA strand scission.
Main Methods:
- In vitro reaction of superhelical Col E1 DNA with syn- and anti-BPDEs.
- Agarose gel electrophoresis to detect DNA strand breaks.
- Electron microscopy for visualization of DNA modification.
- Kinetic analysis to determine reaction mechanisms.
Main Results:
- Syn- and anti-BPDEs induced a concentration-dependent nicking of superhelical Col E1 DNA.
- DNA strand scission accounted for less than 1% of the total DNA modification by BPDEs.
- Kinetic data suggest the formation of unstable phosphotriester intermediates.
Conclusions:
- BPDEs can directly cause DNA strand breaks through a minor modification pathway.
- The hydrolysis of unstable phosphotriesters is the likely mechanism for BPDE-induced DNA nicking.
- This DNA strand scission pathway, though minor, contributes to the genotoxicity of benzo[a]pyrene.