The protein encoded by this gene belongs to the eukaryotic CX(9)C family, characterized by four cysteine residues forming disulfide linkages that create a CHCH fold. In response to stress, it moves from the mitochondrial intermembrane space to the nucleus, where it binds to a conserved oxygen-responsive element in the promoter of cytochrome oxidase 4I2, a subunit of the electron transport chain. Along with recombination signal sequence-binding protein J, this protein activates the element at low oxygen levels. It also acts as a negative regulator of mitochondria-mediated apoptosis; under apoptotic stress, its mitochondrial levels decrease, allowing BCL2-associated X protein to activate the caspase cascade. Pseudogenes of this gene exist on multiple chromosomes, and alternative splicing produces multiple transcript variants.