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Oxidized apurinic/apyrimidinic sites formed in DNA by oxidative mutagens
1Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298.
Abstract:
Treatment of DNA with any of several agents, including ionizing radiation, hydrogen peroxide, bleomycin, neocarzinostatin and the copper (I) chelate complex of 1,10-phenanthroline, produces apurinic/apyrimidinic (AP) sites containing oxidized deoxyribose moieties. These AP sites, which are formed by specific or nonspecific free-radical attack on deoxyribose, have been shown to involve oxidation of deoxyribose at the C-1', C-2' or C-4' position. Oxidized AP sites are generally more susceptible to chemical cleavage than normal AP sites, but are in some cases resistant to cleavage by repair AP endonucleases. Nearly all of the AP sites produced by neocarzinostatin, and a fraction of those produced by bleomycin, are accompanied by closely opposed breaks in the complementary strand. Sequence specificity data strongly implicate oxidized AP sites in neocarzinostatin-induced mutagenesis. The role of AP sites in mutagenesis by the other oxidative mutagens is less clear, although there is in some cases suggestive evidence for such a role.
Insights
Oxidative DNA damage creates apurinic/apyrimidinic (AP) sites, often with oxidized deoxyribose. These modified AP sites influence DNA repair and mutagenesis, particularly with agents like neocarzinostatin.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- DNA damage can occur through various agents, including ionizing radiation and chemical mutagens.
- Apurinic/apyrimidinic (AP) sites are common DNA lesions resulting from base loss.
- Oxidative stress can lead to modified DNA bases and backbone damage.
Purpose of the Study:
- To investigate the formation and characteristics of oxidized apurinic/apyrimidinic (AP) sites in DNA.
- To determine the role of these oxidized AP sites in DNA repair and mutagenesis.
- To understand the mechanism of DNA damage induced by specific oxidative agents.
Main Methods:
- Treatment of DNA with oxidative agents such as ionizing radiation, hydrogen peroxide, bleomycin, neocarzinostatin, and a copper chelate complex.
- Analysis of DNA lesions, focusing on the formation of AP sites with oxidized deoxyribose moieties.
- Assessment of susceptibility to chemical cleavage and repair AP endonuclease activity.
- Investigation of DNA strand breaks and sequence specificity in mutagenesis.
Main Results:
- Several agents produce AP sites containing oxidized deoxyribose at C-1', C-2', or C-4' positions.
- Oxidized AP sites show altered susceptibility to chemical cleavage and resistance to some repair enzymes.
- Neocarzinostatin and bleomycin generate AP sites associated with complementary strand breaks.
- Oxidized AP sites are implicated in neocarzinostatin-induced mutagenesis, with suggestive evidence for other agents.
Conclusions:
- Oxidized AP sites are significant DNA lesions formed by oxidative damage.
- These lesions possess unique biochemical properties affecting DNA repair pathways.
- Oxidized AP sites play a role in the mutagenic potential of certain oxidative DNA-damaging agents.