RELATIVE REPAIR OF ADENOVIRUS DAMAGED BY SUNLAMP, UV AND γ‐IRRADIATION IN COCKAYNE SYNDROME FIBROBLASTS IS DIFFERENT FROM THAT IN XERODERMA PIGMENTOSUM FIBROBLASTS

The DNA repair capacities of three unrelated Cockayne syndrome (CS) fibroblast strains were compared to that of three unrelated xeroderma pigmentosum (XP) strains for three different DNA damaging agents using a sensitive host cell reactivation (HCR) technique. Adenovirus type 2 (Ad 2) was treated with either UV light, gamma-rays or sunlamp-irradiation and subsequently assayed for its ability to form viral structural antigens (Vag) in the CS and XP strains using immunofluorescent straining. D37 values for the survival of Ad 2 Vag synthesis in the CS and XP strains, expressed as a percentage of those obtained in normal strains, were used as a measure of DNA repair capacity. Percent HCR values in the XP strains XP25RO, XP2BE and XP5BE respectively were lowest for UV (6, 14 and 6%), intermediate for sunlamp-irradiation (18, 32 and 10%) and highest for gamma-irradiation (65, 61 and 60%), whereas for the CS strains CS1BE, CS3BE and CS278CTO respectively, percent HCR values were lowest for UV (26, 30 and 34%), intermediate for gamma-irradiation (61, 64 and 69%) and near normal for sunlamp-irradiation (82, 73 and 89%). These results suggest that the 'spectrum of lesions' which is defectively repaired in CS is not the same as that which is defectively repaired in XP.