Deletion of CDKN1A rescues radiosensitivity of CHIP-depleted cells. A, Immunoblot demonstrating homozygous deletion of CDKN1A in A549 cells as well as knockdown of CHIP using shCHIP-2 or sh-NT. B, A549 (control), A549 p21−/−, A549 CHIP−/− and A549 p21−/−/CHIP−/− cells were treated with indicated doses of IR and survival fractions were plotted as in Fig 1. C–D, Cells mentioned in (B) were treated with 10 Gy and cellular senescence was measured using β-gal staining and quantified (D). Error bars represent the mean ±SD of at least three independent experiments. *, P<0.05; ***, P<0.001.