Cell membrane DNA: a new target for psoralen photoadduct formation

The effects of 8-methoxypsoralen plus long wavelength ultraviolet radiation on cell membrane DNA were examined. Treatment of human lymphocytes with 100 ng/ml 8-methoxypsoralen and 5 J/cm2 UVA led to the formation of 7.1 +/- 3.8 photoadducts per million bases. A monoclonal antibody, specific for 8-methoxypsoralen 4',5'-monoadducts, was used to detect photoadducts in the cell membrane DNA of human lymphocytes and three lymphoblastoid cell lines. Treatment of lymphocytes with 8-MOP and UVA reduced the lymphocyte DNA binding capacity by 56%. Cell membranes of normal lymphocytes were shown to contain three high affinity DNA binding proteins of 28, 59, and 79 kDa, respectively.