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 spe cific for cyclobutane pyrimidine dimers and the other for non-cyclobut ane dimer photoproducts, were detected. The expression of these bindin g activities was found to be variable throughout the animal kingdom: c old-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 ty pes of binding activities. The kinetics of expression (rather than the constitutive presence) of these UV damage-specific DNA-binding activi ties after UV treatment correlate with the cell's capacity for DNA rep air. In addition, cyclobutane pyrimidine dimer-binding activities coul d be detected only in cells with established photoreactivating activit y.