Fig. 1.

Expression of p53 in RKO cells irradiated with UVC. (A) Cells were exposed to either 15 or 30 J/m² or left unirradiated (-), and whole-cell lysates were prepared for Western blotting at the times indicated. (B) Northern blot analysis of p53 expression 4 h after exposure to the indicated doses of UVC. Relative p53 abundance was calculated by densitometry and is expressed as fold increase relative to p53 levels in unirradiated cells. (C) Half-life of the p53 mRNA was calculated by addition of actinomycin D (ActD, 2 μg/ml) to RKO cells 4 h after either UVC irradiation (15 J/m²) or no treatment (untreated), as described (11). Relative p53 mRNA abundance is expressed as fold increase relative to p53 mRNA levels in unirradiated cells. (D) Total, cytoplasmic (Cytopl.), nuclear, and polysomal fractions were prepared for Northern blot analysis 4 h after exposure to UVC (15 J/m²); 18S signals reveal even loading of samples.