Illustration showing hypoxia inducible factor complex (HIF, pink ribbon) and aryl hydrocarbon receptor nuclear translocator (ARNT, purple ribbon) heterodimer binding to the hypoxia response element (HRE) of DNA (deoxyribonucleic acid, yellow). HIF coordinates cellular adaptations to low oxygen stress by regulating transcription in erythropoiesis, angiogenesis and metabolism. Specific recognition of the HRE is determined locally by the arginine DNA-binding residues, shown in stick model.