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Base sequence damage in DNA from X-irradiated monkey CV-1 cells.
J M Feingold1, J Masch, J Maio
1Department of Radiology, Albert Einstein College of Medicine, Bronx, New York 10461.
Summary
X-rays induce DNA fragments with 3'-phosphoryl and 3'-phosphoglycolate ends in primate alpha DNA. These DNA strand breaks are dose-dependent and repaired in monkey cells.
Area of Science:
- Molecular Biology
- Radiation Biology
- Genetics
Background:
- Primate component alpha DNA contains highly repetitive sequences.
- DNA damage can result from ionizing radiation, such as X-rays.
- Understanding DNA damage and repair mechanisms is crucial for cell biology.
Purpose of the Study:
- To characterize the types of 3'-ends generated in DNA fragments after X-ray irradiation of monkey cells.
- To investigate the dose-dependence and repair kinetics of these DNA ends.
Main Methods:
- Isolation of DNA scission fragments from irradiated monkey CV-1 cells.
- 5'-32P-end labeling of DNA fragments.
- High-resolution polyacrylamide gel electrophoresis under denaturing conditions.
- Enzymatic hydrolysis using exonuclease III and T4 polynucleotide kinase.
Main Results:
- Two types of 3'-ends, 3 -phosphoryl and 3 -phosphoglycolate, were identified in X-ray-induced DNA fragments.
- These ends were converted to 3 -OH ends upon enzymatic treatment.
- The induction of these DNA ends was dose-dependent (100-900 Gy).
- The frequency of single-strand breaks in alpha DNA was 8.6 x 10(-7) breaks/nucleotide/Gy.
- The identified DNA ends disappeared with a half-time of 1.6 hours during post-radiation incubation.
Conclusions:
- X-ray irradiation of primate alpha DNA in vivo generates 3 -phosphoryl and 3 -phosphoglycolate ends.
- These DNA damage products are subject to repair mechanisms in animal cells.
- This study offers a novel method for studying X-ray-induced DNA damage and repair in specific DNA sequences.