Persistence of radiation-induced double-strand breaks in the DNA of heated CHO cells.
Chinese hamster ovary cells were either heated at 45 degrees C for 15 min or left unheated immediately prior to irradiation and incubation at 37 or 41 degrees C for 5 h. When cellular DNA was analysed by electrophoresis of double-stranded DNA through agarose gels 5 h after irradiation, DNA fragments presumably resulting from unrepaired DNA double-strand breaks (dsbs) were observed in the DNA of all cells. The frequency of the putative unrepaired dsbs was greater in cells heated at 45 degrees C for 15 min before, or incubated at 41 degrees C for 5 h after irradiation, than in unheated, control cells. Gel electrophoresis results were consistent with a failure of irradiated cells to rejoin dsb completely when heated at 45 degrees C before, or incubated at 41 degrees C for 5 h after irradiation. In contrast, nuclear DNA accessibility studies using either an exogenous or an endogenous endonuclease detected no change in the accessibility of DNA in nuclei from 41 degrees C-heated cells. These DNA accessibility studies indicate that the dsbs observed in the DNA of 41 degrees C-heated cells may not result from an actual failure of irradiated cells to repair radiation-induced dsbs during incubation at 41 degrees C.
Warters
R L
RL
Department of Radiology, University of Utah, Salt Lake City 84132.
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D004247:DNA / Q000528:radiation effects*; D004249:DNA Damage; D006358:Hot Temperature; D013997:Time Factors
D004247:DNA