Apurinic/apyrimidinic endonuclease (APE alias Ref-1) is a multifunctional enzyme involved in DNA repair and redox regulation of transcription factors (e.g., AP-1). It also acts as a repressor of its own and other genes. Recently, it was shown that the level of APE mRNA and protein is enhanced upon treatment of cells with oxidative agents, such as hydrogen peroxide (H(2)O(2)), which gives rise to an adaptive response of cells to oxidative stress. Induction of APE is due to APE promoter activation. To elucidate the mechanism of transcriptional activation of APE by oxidative agents, we introduced mutations into the cloned human APE promoter and checked its activity in transient transfection assays. Here we demonstrate that mutational inactivation of a CREB binding site (CRE) present within the promoter completely abolished APE promoter activation by H(2)O(2), indicating that CREB is required for APE induction. The CRE element in the context of the APE promoter sequence binds c-Jun and ATF-2, which was shown in gel retardation experiments. Under conditions of induction of APE by H(2)O(2), the expression of c-Jun was significantly enhanced, which supports the view that induction of c-Jun is involved in signaling leading to APE promoter activation by oxidative stress.
Copyright 1999 Academic Press.