(A) KARP-1 gene expression is induced following x-irradiation. (Left) HCT116 cells were x-irradiated (10 Gy) and then at the indicated times postirradiation RT-PCR reactions followed by Southern hybridizations were performed. (Right) The fold-induction of KARP-1 mRNA was quantitated by using β-actin levels as a reference. (B) KARP-1 induction is dose dependent. (Left) HCT116 cells were x-irradiated at the indicated doses and at 90 min postirradiation RT-PCR reactions followed by Southern hybridizations were performed as described. For the β-actin sample, only the ethidium bromide profile is shown. (Right) The fold-induction of KARP-1 mRNA was quantitated by using β-actin levels as a reference. The average of two independent experiments is shown for A and B. (C) KARP-1 gene expression is induced by other types of DNA damage. (Left) HCT116 cells were x-irradiated (X, 15 Gy) or treated with etoposide (Eto, 1 or 5 μM), UV irradiation (UV, 10 or 20 J/m2), or methyl methanesulfonate (MMS, 1 mM) and then at the indicated times posttreatment RT-PCR reactions followed by Southern hybridizations were performed. (Right) The fold-induction of KARP-1 mRNA was quantitated by using β-actin levels as a reference.