title: Induction of sister chromatid exchanges in xeroderma pigmentosum cells after exposure to ultraviolet light.
abstract: The role of DNA repair mechanisms in the induction of sister chromatid exchanges (SCE) after exposure to ultraviolet radiation was investigated in xeroderma pigmentosum cells. Cells from different excision-deficient XP strains, representing the 5 complementation groups in XP, A, B, C, D and E, and from excision-proficient XP variant strains were irradiated with low doses of UVR (0-3.5 J/m2). The number of SCE was counted after two cycles in the presence of BUdR. In cells of the complementation groups A, B, C and D the number of SCE was significantly higher than in UV-exposed control cells. The frequencies of SCE in group E cells and in XP varient cells were not different from those in control cells. Treatment with caffeine (0-200 microgram/ml) did not result in a different response of variant cells compared with normal cells. A simple correlation between SCE frequency and residual excision-repair activity was not observed. The response of the excision-repair deficient cells suggest that unrepaired damage, produced by UVR is involved in the production of SCE.
mesh_terms: D002110:Caffeine / Q000494:pharmacology; D002460:Cell Line; D003434:Crossing Over, Genetic; D004260:DNA Repair; D006801:Humans; D014466:Ultraviolet Rays; D014983:Xeroderma Pigmentosum / Q000235:genetics*
chemical_list: D002110:Caffeine