Complexes containing activating transcription factor (ATF)/cAMP-responsive-element-binding protein (CREB) interact with the CCAAT enhancer-binding protein (C/EBP)-ATF composite site to regulate Gadd153 expression during the stress response

Gadd153, also known as chop, encodes a member of the CCAAT/enhancer-binding protein (C/EBP) transcription factor family and is transcriptionally activ ated by cellular stress signals. We recently demonstrated that arsenite tre atment of rat pheochromocytoma PC12 cells results in the biphasic induction of Gadd153 mRNA expression, controlled in part through binding of C/EBP be ta and two uncharacterized protein complexes to the C/EBP-ATF (activating t ranscription factor) composite site in the Gadd153 promoter. In this report , we identified components of these additional complexes as two ATF/CREB (c AMP-responsive-element-binding protein) transcription factors having differ ential binding activities dependent upon the time of arsenite exposure, Dur ing arsenite treatment of PC12 cells, we observed enhanced binding of ATF4 to the C/EBP-ATF site at 2 h as Gadd153 mRNA levels increased, and enhanced binding of ATF3 complexes at 6 h as Gadd153 expression declined. We furthe r demonstrated that ATF4 activates, while ATF3 represses, Gadd153 promoter activity through the C/EBP-ATF site. ATF3 also repressed ATF4-mediated tran sactivation and arsenite-induced activation of the Gadd153 promoter. Our re sults suggest that numerous members of the ATF/CREB family are involved in the cellular stress response, and that regulation of stress-induced biphasi c Gadd153 expression in PC12 cells involves the ordered, sequential binding of multiple transcription factor complexes to the C/EBP-ATF composite site .