FIG. 1.

(A) NPM represses p53 transcriptional activity. For the CAT assay, H1299 cells were transfected with the p53 reporter gene construct pG13 CAT and either NPM, p53, or both. The empty pCMV plasmid was used to normalize the plasmid content (6 μg) in all transfections. The cells were harvested 48 h after transfection. The relative CAT activity is expressed as a percentage of the total activity obtained with p53 and pG13 CAT (p53). The data represent the averages of two experiments performed in duplicate, and the error bars correspond to standard errors of the means. (B) Same as panel A except that the cells were transiently transfected with a reporter gene containing five repeats of the p53 binding site from the GADD45 third intron (GADD45 CAT). (C) RKO cells were transiently transfected with pG13 CAT and where indicated with NPM. The cells were exposed to UV radiation (20 J m⁻²) as indicated. (D and E) Up regulation of NPM correlates with p21 down regulation by UV radiation. For Western blot analyses, RKO cells were exposed to the indicated doses of UV radiation and harvested 4 h later. Total cellular protein (40 μg for NPM or 200 μg for p21) was reacted with NPM Ab (D) or p21 Ab (E). Blots were reacted with actin Ab for loading control.