Detection of ionizing radiation-induced DNA double-strand breaks by filter elution is affected by nuclear chromatin structure.
Chinese hamster ovary cells were irradiated with 250 kVp X rays and analyzed for the presence of DNA double-strand breaks using either polycarbonate filter elution or pulsed-field agarose gel electrophoresis at neutral pH. Reduction in DNA length detected by filter elution was produced as a nonlinear function of increasing radiation dose, with a quasi-threshold at low total dose, and as a first-order function of increasing radiation dose as detected by gel electrophoresis. The quasi-threshold observed with filter elution was eliminated when nuclei were isolated from irradiated cells and their chromatin relaxed in a buffer containing low-molarity monovalent cation prior to analysis by filter elution. The results suggest either that the chemical structure of the DNA double-strand breaks produced by low-LET radiation necessitates a DNA relaxation step before they can be detected accurately by filter elution, or that at low total radiation dose a DNA complex forms on the polycarbonate filter.
Warters
R L
RL
Department of Radiology, University of Utah Health Sciences Center, Salt Lake City 84132.
Lyons
B W
BW
D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000528:radiation effects*; D002843:Chromatin / Q000648:ultrastructure*; D006224:Cricetinae; D003412:Cricetulus; D004247:DNA / Q000528:radiation effects*; D004249:DNA Damage; D004260:DNA Repair; D004307:Dose-Response Relationship, Radiation; D004587:Electrophoresis, Agar Gel; D066298:In Vitro Techniques; D011839:Radiation, Ionizing; D012995:Solubility
D002843:Chromatin; D004247:DNA