Analysis of apoptosis induction in Nbs1 deficient cells

Abstract

DNA double strand break (DSB) is the most critical damage that are induced by radiation. Many DSB repair proteins have been identified using several approaches such as positional cloning and phenotype analysis of knockout cells. Among these, Nbs1, the underlying gene for Nijmegen breakage syndrome, forms a complex with Mre11/Rad50 and is essential for homologous recombination (HR) and S-phase check point. To clarify the role of Nbs1 protein on DSB responding pathways, we analyzed apoptosis induction in Nbs1 deficient chicken DT40 cells after irradiation. In sharp contrast to wild type DT40 cells, NBS1 deficient cells did not display apparent induction of apoptosis after exposure to 4 Gy of ¹³⁷Cs gamma-rays. Because DT40 cells are not expressing p53, which acts in apoptosis induction after DNA damage, this result suggests that Nbs1 possesses a critical role on p53 independent apoptosis induction. [J Radiat Res 44:446 (2003)]