(a) Expression of p53 in HUPKI, R175H and HUPKI/R175H heterozygous thymocytes after 5Gy irradiation. Actin was used as the loading control. (b) p53-dependent apoptosis in HUPKI, R175H, HUPKI/R175H, HUPKI/R248W and p53+/− thymocytes 10 hours after treating with 5, 10 and 20Gy of IR. Mean values from three independent experiments are shown with standard deviation. (c) Expression of p53 target genes in HUPKI, R175H/HUPKI and R175H mutant thymocytes 6 hours after 5Gy of IR. mRNA levels of each gene were determined by real time PCR and normalized with the expression of GAPDH. The mRNA levels in the untreated HUPKI MEFs were set to 1.