The induction and repair of lesions produced by the photolysis of (5-4) photoproducts in normal and UV-hypersensitive human cells

A radioimmunoassay was used to study the induction and repair of damage produced by the photolysis of (6-4) photoproducts in normal and UV-sensitive human cells: Photochemical conditions were established to optimize the production of photolyzed (6-4) photoproducts in human cell DNA with minimal induction of other photoproducts. The repair of this photoproduct, presumed to be a Dewar pyrimidinone, was similar to that determined for the (6-4) photoproducts, with most of the antibody-binding sites removed within 4 h post-photolysis. Whereas xeroderma pigmentosum group A cells were deficient in the repair of this lesion, an XP variant and two cell lines selectively hypersentitive to UVB-irradiation were shown to have normal repair. The radioimmunoassay was further used to demonstrate the alkali-lability of the (6-4) photolysis product.