Requirement of ATP for specific incision of ultraviolet-damaged DNA during excision repair in permeable human fibroblasts

Studies from several laboratories have shown that ATP is required for DNA excision repair in UV-irradiated mammalian cells. Using permeable human fibroblasts, we have investigated this ATP requirement in detail. We find that ATP is required for specific incision of UV-damaged DNA in permeable cells. No ATP-independent incision is seen in UV-irradiated permeable xeroderma pigmentosum (complementation group G) fibroblasts, indicating that the ATP-dependent incision observed in normal cells is part of the normal excision repair process. We conclude that, in mammalian cells, ATP is required for specific incision of UV-damaged DNA or for some obligatory step preceding incision in the excision repair pathway. ATP also protects the permeable cells from loss of the capacity to perform excision repair, probably in a non-specific fashion. The actual synthesis of repair patches can proceed in the absence of ATP; however, our data do not exclude the possibility that ATP can also stimulate repair synthesis directly.