IMMUNOCHEMICAL DETECTION OF SEQUENCE-SPECIFIC MODIFICATIONS TO DNA INDUCED BY UV-LIGHT

Sequence specificity of antibodies to UV-damaged DNA has not been desc ribed previously. The antisera investigated here were specific for UV- modified DNA and were absolutely dependent upon the presence of thymin e residues. Using a series of oligonucleotides in competition ELISA, i ncreased inhibition was observed with increasing chain length of UV-po lythymidylate. A minimum of three adjacent thymines was required for e ffective inhibition; alone, dimers of thymine were poor antigens. Alth ough UV-irradiated poly(dC) was not antigenic, cytosines could partial ly replace thymines within the smallest effective epitope (T-T-T) with a high degree of sequence specificity, not previously described. The main epitope induced by UV was formed from adjacent thymines and eithe r a 3' or a 5' pyrimidine.