Nuclear xenobiotic receptor CAR activates transcription of the CYP2B6 gene by directly binding to the distal enhancer PB responsive enhancer module (PBREM). This CAR-mediated activation is synergized by transcription factors early growth response 1 (EGR1) and hepatocyte-enriched nuclear factor 4α (HNF4α) that bind to the proximal element OA response element KI (OARE KI) Inoue, K., & Negishi, M. (2008). Nuclear receptor CAR requires early growth response 1 to activate the human cytochrome P450 2B6 gene. J. Biol. Chem. 283, 10425–10432. Two additional EGR1 binding sites have now been found just downstream from PBREM. Internal deletion of EGR1 sites within the context of the −1.8 kb CYP2B6 promoter, which contains both PBREM and OARE KI, revealed that the distal and proximal EGR1 sites are essential for EGR1 to synergize CAR-mediated transcription. Chromatin conformation capture 3C assays demonstrated that ERG1 may loop the distal PBREM towards the proximal OARE KI so that together, CAR and HNF4α synergistically activate the CYP2B6 promoter.