SEPARATION OF PROTEIN FACTORS THAT CORRECT THE DEFECTS IN THE 7 COMPLEMENTATION GROUPS OF XERODERMA-PIGMENTOSUM CELLS

We fractionated HeLa cell extracts by gel filtration and then micro-in jected them into cells derived from the seven complementation groups ( A-G) of xeroderma pigmentosum (XP), Distinct fractions that corrected the unscheduled DNA synthesis (UDS) of the complementation group XP ce lls were identified. The apparent molecular weights corresponding to c omplementation groups A, B, C, D, E, F, and G were estimated to be 80, 600, 600, 240, 100, 240, and 280 kDa, respectively, These factors wer e stable in the respective cell lines, the shortest half life being 16 h for the XP-A and XP-G; complementing factors, The fraction (80 kDa) that corrected the UDS in XP-A cells also complemented the defect of the XP-A cell extract in the incision of DNA containing a pyrimidine d imer in a cell-free system. The separated fractions will be useful for understanding the molecular nature of these factors and for assigning complementation groups of cells derived from suspected XP patients.