INDUCTION OF DNA BREAKAGE IN X-IRRADIATED NUCLEOIDS SELECTIVELY STRIPPED OF NUCLEAR PROTEINS IN 2 MOUSE LYMPHOMA CELL-LINES DIFFERING IN RADIOSENSITIVITY

The role of nuclear proteins in protection of DNA against ionizing rad iation and their contribution to the radiation sensitivity was examine d by an alkaline version of comet assay in two L5178Y (LY) mouse lymph oma cell lines differing in sensitivity to ionizing radiation, LY-S ce lls are twice more sensitive to ionizing radiation than LY-R cells (Do values of survival curves are 0.5 Gy and 1 Gy, respectively). Sequent ial removal of nuclear proteins by extraction with NaCl of different c oncentrations increased the X-ray induced DNA damage in LY-R nucleoids . In contrast, in the radiation sensitive LY-S cell line, depletion of nuclear proteins practically did not affect DNA damage. Although ther e is no doubt that the main cause of LY-S cells' sensitivity to ionizi ng radiation is a defect in the repair of double-strand breaks, our da ta support, the concept that nuclear matrix organisation may contribut e to the cellular susceptibility to DNA damaging agents.