ALTERED ELECTROPHORETIC BEHAVIOR OF DNA DUE TO SHORT-TIME UV-B IRRADIATION

UV-B irradiation is often inevitable for visualization of DNA fragment s after ethidium bromide staining. Three different simple-repeat-conta ining, double-stranded genomic DNA fragments were analyzed for UV-B (3 12 nm) damage using different gel electrophoretic systems. The effects of UV-B light were obvious after 5 min (31.5 kJ/m(2)) of irradiation in native polyacrylamide gel electrophoresis (PAGE). Standard single-s trand conformation analyses revealed no alterations while a modificati on did. Sodium dodecyl sulfate (SDS)-PAGE was found to be highly sensi tive with regard to the detection of damages and their time/dosage dep endency. In addition, SDS-PAGE analysis pointed to different events oc curring during UV-B irradiation. Alterations in DNA conformation were detected in every single strand analyzed after 1 min (6.3 kJ/m(2)) of UV-B exposure. Gel retardation analyses revealed significant changes o f protein binding to target DNAs after 2 min of irradiation - possibly stemming from structural modifications and/or originating from bindin g sites for proteins involved in DNA repair.