Inhibition of transcription factor binding by ultraviolet-induced pyrimidine dimers

The formation of DNA photoproducts by ultraviolet (UV) light is responsible for the induction of mutations and the development of skin cancer. Cis-syn cyclobutane pyrimidine dimers (pyrimidine dimers) are the most frequent lesions produced in DNA by UV irradiation. Besides being mutagenic, pyrimidine dimers may interfere with other important DNA-dependent processes. To analyze the effects of pyrimidine dimers on the ability of DNA sequences to be recognized by trans-acting factors, we have incorporated site-specific T-T dimers into oligonucleotides containing the recognition sequences of the sequence-specific transcription factors E2F, NF-Y, AP-1, NF kappa B, and p53. In each case, presence of the photodimer strongly inhibited binding of the respective transcription factor complex. Reduction of binding varied between 11- and 60-fold. The results indicate that the most common UV-induced DNA lesion can interfere severely with binding of several important cell cycle regulatory and DNA damage responsive transcription factors. We suggest that inhibition of transcription factor binding may be a major biological effect of UV radiation since promoter regions are known to be repaired inefficiently and since UV damage can deregulate the function of a large number of different factors.