Biological Response to Ionizing Radiation in Mouse Embryo Fibroblasts with a Targeted Disruption of the DNA Polymerase β Gene

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Abstract
Miura, M., Watanabe, H., Okochi, K., Sasaki, T. and Shibuya, H. Biological Response to Ionizing Radiation in Mouse Embryo Fibroblasts with a Targeted Disruption of the DNA Polymerase β Gene. Base excision repair (BER) is carried out by two distinct pathways in mammalian cells, one dependent on DNA polymerase β (Polb) and the other on proliferating cell nuclear antigen (Pcna). We studied whether the Polb-dependent pathway plays an important role in BER in vivo after exposure to ionizing radiation. For this purpose, we used mouse embryo fibroblasts derived from wild-type and Polb gene knockout littermates. Both cell lines had essentially the same clonogenic cell survival and low levels of apoptosis as determined by a colony formation assay and by a change in mitochondrial membrane potential, respectively. No significant cleavage of protein kinase C δ (Pkcd) in vivo, which is a substrate for caspase 3, was detected, and intact Pkcd was retained in both cell lines for at least 72 h after irradiation....