P53-INDEPENDENT DNA-REPAIR AND CELL-CYCLE ARREST IN EMBRYONIC STEM-CELLS

The role of p53 in DNA repair and cell cycle checkpoint after ultravio let irradiation was investigated in an embryonic stem cell line homozy gous for a targeted deletion of p53, Results indicate that loss of p53 does not alter the capacity of ES cells to respond to DNA damage. wil d-type and p53-deficient cells showed similar cessation of DNA synthes is after UV damage and similar ultimate capacity to repair a transient ly transfected reporter plasmid, Interestingly, in the absence of DNA damaging treatment, the transit of p53-deficient cells through S phase mas slower than wild-type cells. We suggest that this may result from the absence of a p53-dependent response to endogenous DNA damage: wit hout p53 sensing endogenous damage leading to immediate repair, such d amage may persist and thus delay DNA synthesis. (C) 1998 Federation of European Biochemical Societies.