Repair of gamma-ray-induced base damage in L5178Y sublines is damage type-dependent and unrelated to radiation sensitivity

The L5178Y (LY) murine lymphoma sublines LY-R and LYS are differentially se nsitive to ionizing radiation. The high radiation sensitivity of LYS cells is related to impaired rejoining of DNA double strand breaks. We found prev iously that the gamma -ray-induced base damage is higher in the more radios ensitive LYS subline. Here, we examine the role of the repair of ionizing r adiation induced base damage in relation to the radiosensitivity difference of these sublines. We used the GS/MS technique to estimate the repair rates of six types of ba se dam age in gamma -irradiated LY cells. Ah modified DNA bases identified in the course of this study were typical for irradiated chromatin. The tota l amount of initial base damage was higher in the radiation sensitive LYS s ubline than in the radiation resistant LY-R subline. The repair rates of 5- OHMeUra, 5-OHCyt, 8-OHAde were similar in both cell lines, the repair rates of FapyAde and 8-OHGua were higher in the radiosensitive LYS cell line, wh ereas the repair of 8-OHUra was faster in its radioresistant counterpart, t he LY-R. Altogether, the repair rates of the gamma -ray-induced DNA base damage in L Y sublines are related neither to the initial amounts of the damaged bases nor to the differential lethal or mutagenic effects of ionizing radiation i n these sublines.