INDUCIBLE REPAIR OF THYMINE GLYCOL DETECTED BY AN ULTRASENSITIVE ASSAY FOR DNA-DAMAGE

An ultrasensitive assay for measuring DNA base damage is described tha t couples immunochemical recognition with capillary electrophoresis an d laser-induced fluorescence detection. The method provides a detectio n limit of 3 x 10(-21) moles, an improvement of four to five orders of magnitude over current methods. Induction and repair of thymine glyco ls were studied in irradiated A549 cells (a human lung carcinoma cell line). Exposure of these cells to a low dose of radiation (0.25 Gray) 4 hours before a clinically relevant dose (2 Gray) enhanced removal of thymine glycols after the higher dose. These data provide evidence fo r an inducible repair response for radiation-induced damage to DNA bas es.