Inhibition of DNA damage–induced cell-cycle arrest and p53 activation after knockdown of CXXC5 in OCI-AML3 cells. Cells were stably infected with lentiviral CXXC5 shRNA (shR) or scrambled control (co) and irradiated with 4 Gy. (A) Reduced and delayed G1 and G2 arrest after irradiation compared with controls. A representative figure is shown. Numbers in bars correspond to percentages of cells. (B) Decreased upregulation of p53 protein 4 hours after irradiation compared with control as determined by Western blot. A representative blot is shown. The 2 bands for CXXC5 correspond to the 24-kDa and 33-kDa isoforms. (C) Decreased upregulation and nuclear localization of p53 protein 4 hours after irradiation compared with control in confocal microscopy. Representative images are shown. Original magnification ×60 for all images.