ARNT-HIF transcription factor with coactivator, illustration. Hypoxia-inducible factor complex (HIF) and aryl hydrocarbon receptor nuclear translocator (ARNT, yellow) require association with several transcription coactivators for a successful cellular response to hypoxic stress. Here, coiled-coil coactivators (CCC, pink) form a complex with ARNT and endothelial PAS domain-containing protein (EPAS, blue).These transcription coactivators play essential roles in the HIF-dependent hypoxia response. CCC misregulation is associated with several forms of cancer.