FIG. 2.
p53 expression and transcriptional activity after X irradiation. (A) X-ray (12 Gy) treatment stabilized p53 in Rat-1 cells 24 h after irradiation, although to a lesser extent than UVC. (B) Rat-1 cells fail to express p21WAF1/CIP1 protein after X irradiation or UVC treatment, whereas REF52 cells, which arrest in G1 after X irradiation, exhibit increasing induction of p21WAF1/CIP1 at 2 and 24 h postirradiation, respectively. (C) X-ray (12 Gy) treatment induces MDM2 in Rat-1 cells in a p53-dependent manner, as shown by the abrogation of this response by expression of a dominant negative p53 in Rat-1-DN10 cells. Sizes are indicated in kilodaltons.