Differential Expression of Pyrimidine Dimer‐binding Proteins in Normal and Uv Light‐treated Vertebrate Cells

The expression of UV damage-specific DNA-binding proteins was examined in various phylogenetically distant species with differing DNA repair phenotypes. Two distinct constitutive DNA-binding activities, one specific for cyclobutane pyrimidine dimers and the other for non-cyclobutane dimer photoproducts, were detected. The expression of these binding activities was found to be variable throughout the animal kingdom: cold-blooded vertebrates show a constitutive cyclobutane dimer-binding activity exclusively, and primates reveal only non-cyclobutane binding activity. In contrast, birds and marsupials appear to express both types of binding activities. The kinetics of expression (rather than the constitutive presence) of these UV damage-specific DNA-binding activities after UV treatment correlate with the cell's capacity for DNA repair. In addition, cyclobutane pyrimidine dimer-binding activities could be detected only in cells with established photoreactivating activity.