FANCONIS ANEMIA CELLS HAVE NORMAL STEADY-STATE LEVELS AND REPAIR OF OXIDATIVE DNA-BASE MODIFICATIONS SENSITIVE TO FPG PROTEIN

Cells from Fanconi's anaemia (FA) patients are abnormally sensitive to oxygen. However, a distinct genetic defect in either the cellular def ence against reactive oxygen species (ROS) or in their metabolic gener ation has not been identified to date. Recently, the gene for the huma n 8-hydroxyguanine (8-oxoG) glycosylase, which removes this oxidative base modification from the genome, has been localized on chromosome 3p 25, i.e., in the same region as the FA complementation group D (FAD) g ene, We therefore studied the removal of photosensitization-induced 8- oxoG residues from the DNA of FA cells, using Fpg protein, the bacteri al 8-oxoG glycosylase, to quantify the lesions by alkaline elution. Si milar repair kinetics (approx. 50% removal within 2 h) were observed i n Epstein-Barr virus (EBV) immortalized lymphoid cells from FA complem entation groups A, B, C and D and in control cells from normal donors, as well as in primary fetal lung fibroblasts not yet assigned to a sp ecific complementation group. The susceptibility for the induction of oxidative DNA modifications by photosensitization was similar in all c ells. In addition, the background (steady-state) levels of Fpg-sensiti ve oxidative DNA base modifications, which reflect the balance between generation and removal of the lesions, were similar in control and FA cells. It is concluded that both the generation and the overall remov al of 8-oxoG residues in nuclear DNA is not impaired in FA cells. (C) 1998 Elsevier Science B.V. All rights reserved.