Transcriptional activation of apurinic/apyrimidinic endonuclease (Ape, Ref-1) by oxidative stress requires CREB

Apurinic/apyrimidinic endonuclease (APE alias Ref-l) is a multifunctional e nzyme 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. Recen tly, it was shown that the level of APE mRNA and protein is enhanced upon t reatment of cells with oxidative agents, such as hydrogen peroxide (H2O2), which gives rise to an adaptive response of cells to oxidative stress. Indu ction of APE is due to APE promoter activation. To elucidate the mechanism of transcriptional activation of APE by oxidative agents, we introduced mut ations into the cloned human APE promoter and checked its activity in trans ient transfection assays. Here we demonstrate that mutational inactivation of a CREB binding site (CRE) present within the promoter completely abolish ed APE promoter activation by H2O2, indicating that CREB is required for AP E induction. The CRE element in the context of the APE promoter sequence bi nds c-Jun and ATF-2, which was shown in gel retardation experiments. Under conditions of induction of APE by H2O2, the expression of c-Jun was signifi cantly enhanced, which supports the view that induction of c-Jun is involve d in signaling leading to APE promoter activation by oxidative stress. (C) 1999 Academic Press.