Hypoxia inducible factors bound to DNA, molecular model. Hypoxia inducible factors (HIF) proteins bind to DNA (deoxyribonucleic acid) and regulate physiological responses to low oxygen stress. HIF (pink ribbon) and aryl hydrocarbon receptor nuclear translocator (ARNT, purple ribbon) combine and bind to the hypoxia response element (HRE) section of DNA (yellow double helix). Specific recognition of the HRE is determined locally by the DNA-binding arginine residues (shown in stick model). HIFs coordinate cellular adaptations to low oxygen stress by regulating gene transcription activity.