Figure 4
Δ122p53 stabilizes mΔpro and enhances its ability to induce a cell cycle arrest after DNA damage. (a) Bone marrow from Δ122p53/mΔpro mice induced a cell cycle arrest response following DNA damage. Bone marrow was isolated from 4 to 6-week-old mice of indicated genotypes, cultured and treated with 0.2 μg/ml amsacrine. After 24 h, cells were pulse-labeled with BrdU, harvested, fixed, and stained with a fluorescent antibody to BrdU and the percentage of BrdU-positive cells was measured by flow cytometry. Bone marrow from mice with various combinations of the Δ122p53, mΔpro, wild-type (+), or p53 null (-) alleles were included for comparison. ****P<0.0001, ***P<0.001, **P<0.01, *P<0.05 in comparison with p53+/+ treated. Results are represented as the mean±S.D.; n=6 mice per genotype. (b) The presence of the Δ122p53 allele, stabilized mΔpro after DNA damage. Splenocytes from Δ122p53/mΔpro and mΔpro/- mice were cultured, exposed to 1 μg/ml amsacrine and western blots carried out with an antibody to the N terminus of p53 to detect mΔpro. (c) The presence of the Δ122p53 allele led to increased Ser18 phosphorylated mΔpro (left) and increased p21CIP1 (right) in response to DNA damage. Splenocytes from Δ122p53/mΔpro and mΔpro/- mice were cultured, exposed to 1 μg/ml amsacrine and western blots carried out with an antibody to phosphorylated Ser18 on p53 or p21CIP1. All experiments were carried out at least three times
