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Constraints to DNA unwinding near radiation-induced strand breaks in Ewing's sarcoma cells
T J Jorgensen1, S C Prasad, T P Brennan
1Department of Radiation Medicine, Vincent T. Lombardi Cancer Research Center, Georgetown University Medical Center, Washington, D.C. 20007.
Abstract:
Ewing's sarcoma cell lines were compared to other cell lines for induction of DNA strand breaks by ionizing radiation and their ability to repair those breaks. The alkali-unwinding assay and alkaline sucrose gradient analysis were used for these studies. The alkali-unwinding assay revealed that the amount of DNA unwound per strand break in Ewing's sarcoma cells was less than for other cells and was not influenced by high-salt denaturation conditions. Ewing's sarcoma cells had similar induction and repair rates for strand breaks compared with other cell lines. The kinetics of unwinding suggests there are constraints to DNA unwinding in the chromatin of Ewing's sarcoma cells, possibly related to high levels of poly(ADP-ribose) polymerase in these cells.