A Report Summary

Fusion between HeLa and fibroblasts from complementation group D xeroderma pigmentosum (XPD) followed by challenge with small doses of ultraviolet light (u.v.) results in the production of hybrid cells expressing either HeLa (HD1) or XPo-like (HD2) sensitivity to u.v. and related repair capacity. Assays used include unscheduled DNA synthesis (UDS), DNA break accumulation in the presence of inhibitors of DNA repair synthesis and host cell reactivation of irradiated adenovirus. Complementation assay in heterokaryons reveals limited ability of HD2 to restore UDS in X P D nuclei. We believe this complementation is more apparent than real since proliferating hybrids of HD2 and X P D parentage are without exception u.v.-sensitive and express limited excision repair. On the other hand hybrids between HD2 and XPc, X P E or X P F fibroblasts show true complemen-tation resulting in a return to normal u.v. sensitivity and elevated repair ability