DCAF12 promotes apoptosis and inhibits NF-kappa B activation by acting as an endogenous antagonist of IAPs

Members of the Inhibitor of Apoptosis Protein (IAP) family are essential for cell survival and appear to neutralize the cell death machinery by binding pro-apoptotic caspases. dcaf12 was recently identified as an apoptosis regulator in Drosophila. However, the underlying molecular mechanisms are unknown. Here we revealed that human DCAF12 homolog binds multiple IAPs, including XIAP, cIAP1, cIAP2, and BRUCE, through recognition of BIR domains in IAPs. The pro-apoptotic function of DCAF12 is dependent on its capacity to bind IAPs. In response to apoptotic stimuli, DCAF12 translocates from the nucleus to the cytoplasm, where it blocks the interaction between XIAP and pro-apoptotic caspases to facilitate caspase activation and apoptosis execution. Similarly, DCAF12 suppresses NF-kappa B activation in an IAP binding-dependent manner. Moreover, DCAF12 acts as a tumor suppressor to restrict the malignant phenotypes of cancer cells. Together, our results suggest that DCAF12 is an evolutionarily conserved IAP antagonist.