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Effect of ethidium bromide intercalation on DNA radiosensitivity
M Begusová1, M Spotheim-Maurizot, V Michalik
1Centre de Biophysique Moléculaire, CNRS, Orléans, France.
International Journal of Radiation Biology
|February 9, 2000
Summary
Ethidium bromide (EtBr) affects DNA damage differently based on DNA structure. For linear DNA, EtBr offers radioprotection, while for supercoiled plasmids, it modifies damage yields by altering superhelicity.
Area of Science:
- Molecular Biology
- Radiation Biology
- Biochemistry
Background:
- Fast neutrons induce DNA damage, including single-strand breaks (ssb).
- Intercalating drugs like ethidium bromide (EtBr) can modify DNA's response to radiation.
- Understanding these interactions is crucial for radiation protection and therapy.
Purpose of the Study:
- To investigate the impact of ethidium bromide (EtBr) on fast neutron-induced single-strand breaks (ssb).
- To compare the effects on supercoiled pBR322 plasmid DNA versus a linear DNA fragment.
Main Methods:
- Agarose gel electrophoresis to quantify ssb in plasmid DNA.
- Sequencing gel electrophoresis to determine breakage probability at nucleotide sites.
- Calculation of volume variations due to EtBr intercalation.
- Simulation of radio-modifying effects on linear DNA.
Main Results:
- EtBr increased ssb yield in plasmid DNA up to 0.04 drug/bp, then decreased it.
- Linear DNA showed a slight protective effect across all EtBr concentrations.
- The protective effect on linear DNA was uniform across nucleotide sites.
Conclusions:
- Radioprotection in linear DNA by EtBr is primarily due to hydroxyl radical scavenging.
- Radio-modification in supercoiled plasmids is mainly attributed to changes in effective volume and superhelicity caused by EtBr.