Mechanism of diepoxybutane-induced p53 regulation in human cells.

Diepoxybutane (DEB) is the most potent active metabolite of the environmental chemical 1,3-butadiene (BD). BD is a known mutagen and human carcinogen and possesses multisystems organ toxicity. We previously reported the elevation of p53 in human TK6 lymphoblasts undergoing DEB-induced apoptosis. In this study, we have characterized the DEB-induced p53 accumulation and investigated the mechanisms by which DEB regulates this p53 accumulation. The elevation of p53 levels in DEB-exposed TK6 lymphoblasts and human embryonic lung (HEL) human fibroblasts was found to be largely due to the stabilization of the p53 protein. DEB increased the acetylation of p53 at lys-382, dramatically reduced complex formation between p53 and its regulator protein mdm2 and induced the phosphorylation of p53 at serines 15, 20, 37, 46, and 392 in human lymphoblasts. A dramatic increase in phosphorylation of p53 at serine 15 in correlation to total p53 levels was observed in DEB-exposed Ataxia Telangiectasia Mutated (ATM) proficient human lymphoblasts as compared to DEB-exposed ATM-deficient human lymphoblasts; this implicates the ATM kinase in the elevation of p53 levels in DEB-exposed cells. Collectively, these findings explain for the first time the mechanism by which p53 accumulates in DEB-exposed cells and contributes to the understanding of the molecular toxicity of DEB and BD.