Depletion of CHIP enhances stability of p21. A–B, RT-qPCR of p21 of CHIP proficient (sh-NT) and knockdown (shCHIP-2) of A549 and H1299 cells treated with or without 10 Gy. C, A549 and E, H1299 cells (sh-NT or shCHIP-2), were subjected to 0 or 10 Gy and 24h later cells were treated with 100 μg/mL cycloheximide (CHX) and harvested as indicated time points. Lysates were immunoblotted for CHIP, p21 and tubulin as loading control. D, F, Remaining amount of p21 (normalized with corresponding 0h) was plotted for A549 (D) and H1299 (F). G, A549 cells were infected with retrovirus containing empty vector or wt-CHIP, treated as C. H, Remaining amount of p21 from G calculated as in D. Experiments D, F and H represents the mean ±SD of at least three independent experiments. *, P<0.05; **, P<0.01; ***, P< 0.001.