DNA Excision Repair in Cell Extracts from Human Cell Lines Exhibiting Hypersensitivity to DNA-damaging Agents

Whole cell extracts from human lymphoid cell lines can perform in vitro DNA repair synthesis in plasmids damaged by agents including L'Y or r/i-diamminedichloroplatinum(II) (cii-DDP). Kxtracts from xeroderrna pigmentosum (\l'i cells are defective in repair synthesis. \Ve have non studied in vitro DNA repair synthesis using extracts from lymphoblastoid cell lines representing four human hereditary syndromes with increased sensitivity to DNA-damaging agents. Extracts of cell lines from individuals with the sunlight-sensitive disorders dysplastic nevus syn drome or Cockayne's syndrome (complementation groups A and B) showed normal DNA repair synthesis in plasmids with I \ photoproducts. This is consistent with in vivo measurements of the overall DNA repair capacity in such cell lines. A number of extracts were prepared from two cell lines representing the variant form of XP (\P-V). Half of the extracts prepared showed normal levels of in vitro DNA repair synthesis in plasmids containing I \ lesions, but the remainder of the extracts from the same cell lines showed deficient repair synthesis, suggesting the possibility of an unusually labile excision repair protein in XP-V. Fanconi's anemia (FA) cells show cellular hypersensitivity to cross-linking agents including <n-1 >I>I'. Kxtracts from cell lines belonging to two different complementation groups of FA showed normal DNA repair synthesis in plasmids containing c/j-DDP or IV adducts. Thus, there does not appear to be an overall excision repair defect in FA, but the data do not exclude a defect in the repair of interstrand DNA cross links.