title: DNA-protein cross-linking by ultraviolet radiation in normal human and xeroderma pigmentosum fibroblasts.
abstract: DNA-protein cross-linking by ultraviolet radiation was measured in human fibroblasts by an adaptation of the method of DNA alkaline elution. To measure cross-linking, a controlled frequency of DNA single-strand breaks was introduced by exposing the cells to a low dose of X-ray at 0 degrees C prior to analysis by alkaline elution. The effect of prior exposure of the cells to ultraviolet radiation was to reduce the rate and/or extent of DNA elution from X-irradiated cells. This effect was attributed to DNA-protein cross-linking, since the effect was reversed by treatment of the cell lysates with proteinase-K. Cross-linking in normal human fibroblasts occurred immediately after ultraviolet irradiation, prior to the appearance of DNA single-strand breaks due to excision repair. Upon incubation of normal cells after exposure, to ultraviolet radiation, the cross-linking was partially repaired. In xeroderma pigmentosum cells, cross-links appeared as in normal cells, but there was no repair. Instead, the extent of cross-linking appeared to increase upon incubation after ultraviolet irradiation.
mesh_terms: D001665:Binding Sites; D004247:DNA / Q000378:metabolism / Q000528:radiation effects*; D003852:Deoxyribonucleoproteins; D004307:Dose-Response Relationship, Radiation; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism / Q000528:radiation effects*; D011830:Radiation Effects; D014466:Ultraviolet Rays; D014983:Xeroderma Pigmentosum / Q000378:metabolism*
chemical_list: D003852:Deoxyribonucleoproteins; D011506:Proteins; D004247:DNA