Figure 2. Cd increases p53 protein levels by suppressing UBE2D2 and UBE2D4 gene expression in HK-2 cells.

(a) Knockdown efficiency of UBE2D2 and UBE2D4 genes in HK-2 cells by UBE2D2 and UBE2D4 siRNA treatment. UBE2D2 and UBE2D4 siRNAs were added to HK-2 cells for 24 h. mRNA levels were examined using real-time RT-PCR. mRNA levels were normalized to GAPDH. Values are the mean ± S.D. (n = 3). *Significantly different from the corresponding control group, P < 0.05. (b) p53 protein levels in UBE2D2 and UBE2D4 double knockdown HK-2 cells. Whole cell lysates of HK-2 cells treated with UBE2D2 and UBE2D4 siRNAs for 24 h or 40 μM Cd (CdCl₂) for 3 h were used for western blotting and probed with p53 antibody. Anti-GAPDH antibody was used as the loading control. Upper panel, p53; lower panel, GAPDH. The two blots were run under the same experimental conditions. Uncropped images are provided in Supplementary Fig. 1c.