Fig. 5. Induction of p53 by DNA damage is faster and leads to higher p53 levels in the revertants (HA and HF) than in HeLa cells. Cells were induced with 0.45 nM of actinomycin D (ACTD) for 0, 12, and 24 h before lysis. Western blot analyses were performed using 25 µg of total cell lysate and probed with an anti-p53-specific antibody (DO-1). FS-4-human foreskin fibroblasts and Saos-2 cells were used as a positive and negative control for p53 induction, respectively.