Figure 1.

Optimization of in vitro repair assay. Reaction mixtures (20 μl) containing control and damaged DNA substrates were incubated with increasing amounts of nuclear extract prepared from normal human fibroblast cells (GM1310B). The reactions were incubated at 30°C for 1 h. The samples were then subjected to RNAse A and proteinase K digestion. After extraction with organic solvents and ethanol precipitation, the plasmid DNA samples were linearized with EcoRI and resolved on a 0.75% agarose gel. The agarose gel was dried under heated vacuum, and the bands containing radioactively labeled DNA were quantified on a PhosphorImager (Molecular Dynamics).