Relationship of DNA Repair and Chromosome Aberrations to Potentially Lethal Damage Repair in X-Irradiated Mammalian Cells
By the alkaline elution technique, the repair of x-ray-induced DNA single strand breaks and DNA-protein cross-links was investigated in stationary phase, contact-inhibited mouse cells. During the first hour of repair, approximately 90% of x-ray induced single strand breaks were rejoined whereas most of the remaining breaks were rejoined more slowly during the next 5 hr. The number of residual non-rejoined single strand breaks was approximately proportional to the x-ray dose at early repair times. DNA-protein cross-links were removed at a slower rate — T½ approximately 10–12 hr. Cells were subcultured at low density at various times after irradiation and scored for colony survival (potentially lethal damage repair), and chromosome aberrations in the first mitosis after sub-culture. Both cell lethality and the frequency of chromosome aberrations decreased during the first several hours of repair, reaching a minimum level by 6 hr; this decrease correlated temporally with the repair of the slowly rejoining DNA strand breaks. The possible relationship of DNA repair to changes in survival and chromosome aberrations is discussed.
KeywordsChromosome Aberration Linear Energy Transfer Repair Time Ataxia Telangiectasia Nitrogen Mustard
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