Estimates of the rate of ligation during excision repair of ultraviolet-damaged DNA in mammalian cells.

When ultraviolet-irradiated mammalian cells are incubated with inhibitors of repair DNA synthesis, incomplete repair sites--seen as DNA breaks--accumulate. If the inhibition is reversed, the breaks are joined. Thus the ligation step of excision repair can be investigated. With aphidicolin as inhibitor, ligation occurs at up to 15-times the rate of incision. 3-Aminobenzamide (which inhibits poly(ADPribose) synthesis) does not delay the rejoining of DNA breaks.