DNA damage, micronucleus formation, and cell death from 125I decays in DNA.
CHO cells were pulse-labeled with 125I-iododeoxyuridine, harvested 30 min or 5 h after labeling, and stored at -196 degrees C for accumulation of 125I decays. The 30- min groups yielded low-LET survival curves (large shoulder, D0 136 decays/cell); 5-h groups showed a high-LET pattern of cell killing (no shoulder, D0 45 decay/cell). Surprisingly, the shift in 125I action was abolished in cells exposed to HAT medium; both 30-min and 5-h cell groups exhibited high-LET-type killing (no shoulder, D0 52 decays/cell). The striking difference in cell death was not accompanied by any change in induction or repair of DNA DSBs, but the pattern of micronucleus formation (and by implication chromosome damage) did parallel 125I-induced cell death. These findings suggest that cell killing may not be directly linked to the absolute number of DNA DSBs and that damage to higher-order genome structures may be an important factor in radiation-induced cell death.
Hofer
K G
KG
Institute of Molecular Biophysics Florida State University Tallahassee, 32306, USA.
Lin
X
X
Bao
S
S
D000818:Animals; D016466:CHO Cells / Q000187:drug effects / Q000528:radiation effects; D016923:Cell Death; D002470:Cell Survival; D006224:Cricetinae; D003470:Culture Media; D004247:DNA / Q000378:metabolism / Q000528:radiation effects*; D004249:DNA Damage; D007065:Idoxuridine / Q000378:metabolism; D007457:Iodine Radioisotopes / Q000378:metabolism; D018499:Linear Energy Transfer; D015162:Micronucleus Tests; D019384:Nucleic Acid Synthesis Inhibitors / Q000378:metabolism
D003470:Culture Media; D007457:Iodine Radioisotopes; D019384:Nucleic Acid Synthesis Inhibitors; D004247:DNA; D007065:Idoxuridine