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DNA double strand break induction in yeast
J Kiefer1, R Egenolf, S E Ikpeme
1Strahlenzentrum der Justus-Liebig-Universität, Giessen, Germany. juergen.kiefer@strz.uni-giessen.de
Radiation Protection Dosimetry
|August 27, 2002
Summary
Heavy ions induce DNA double-strand breaks (DSBs) in yeast cells. Induction cross-sections vary with linear energy transfer (LET), deviating from simple models and showing unique ion behavior at high LET.
Area of Science:
- Radiation Biology
- Molecular Biology
- Biophysics
Background:
- Accelerated heavy ions are used to study DNA damage.
- Understanding DNA double-strand break (DSB) induction is crucial for radiobiology.
Purpose of the Study:
- To systematically measure DSB induction by heavy ions in diploid yeast cells.
- To compare experimental results with existing theoretical models.
Main Methods:
- Utilized pulsed field gel electrophoresis to separate DNA and measure molecular weight loss.
- Employed a range of ions from protons to uranium with varying Linear Transfer (LET) values.
- Quantified absolute DSB induction without calibration due to known yeast chromosome DNA content.
Main Results:
- DSB induction cross-sections increased with LET, plateauing around 200 keV/µm.
- At higher LET values, ion-specific behaviors emerged, deviating from a single curve.
- Observed a decrease in cross-sections for very heavy particles due to penumbra effects.
- A semi-empirical fit revealed a linear-quadratic dependence of DSB induction on LET up to 1000 keV/µm.
- Relative Biological Effectiveness (RBE) for DSB induction peaked around 2.5 at 200 keV/µm.
Conclusions:
- Classical target theory and track structure models do not fully explain the observed DSB induction patterns.
- Yeast cells exhibit distinct responses to heavy ions compared to mammalian cells, potentially due to chromatin structure differences.
- The findings highlight the complexity of heavy ion-induced DNA damage and the need for refined models.