Ionizing radiation alters the levels of epigenetic regulators in HCT116 cells. (A) RT-PCR was performed to show the mRNA levels of methylation regulatory factors (DNMT1, MBD2, MBD4, and MeCP2) in HCT116 cells irradiated with 2 or 5 Gy, or treated with 5-aza-dC as a control. (B) Western blots show the protein expression levels of DNMT1 and DNMT3b in HCT116 cells irradiated with 2 or 5 Gy, or treated with 5-aza-dC as a control. The blots were probed using anti-DNMT1 (upper panel) and anti-DNMT3b (middle panel) antibodies. GAPDH and anti-β-actin were used for normalization for RT-PCR and western blotting analyses, respectively.