DNA-damage processing in a radiation-sensitive mouse cell line

The induction and repair of radiation-induced DNA damage was assessed in 3 mouse cell lines, including the parental L cell line, a radiation-sensitive, SL3-147 mutant cell line and the H5 revertant to radiation resistance. The yield of neither radiation-induced DNA single- nor double-strand breaks could explain the variable sensitivity of the 3 cell lines. Closure of DNA single-strand breaks proceeded at a similar rate in both the L and SL3-147 cell lines. Closure of DNA double-strand breaks however was significantly slower and less complete in the SL3-147 cell line than in either of the radiation-resistant cell lines. The results are consistent with the increased radiation sensitivity of the SL3-147 cell line resulting from a defect in their ability to repair radiation-induced DNA double-strand breaks.