The nuclear orphan receptor CAR-retinoid X receptor heterodimer activates the phenobarbital-responsive enhancer module of the CYP2B gene

P Honkakoski; I Zelko; T Sueyoshi; M Negishi

doi:10.1128/MCB.18.10.5652

The nuclear orphan receptor CAR-retinoid X receptor heterodimer activates the phenobarbital-responsive enhancer module of the CYP2B gene

Mol Cell Biol. 1998 Oct;18(10):5652-8. doi: 10.1128/MCB.18.10.5652.

Authors

P Honkakoski¹, I Zelko, T Sueyoshi, M Negishi

Affiliation

¹ Pharmacogenetics Section, Laboratory of Reproductive and Developmental Toxicology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA.

Abstract

PBREM, the phenobarbital-responsive enhancer module of the cytochrome P-450 Cyp2b10 gene, contains two potential nuclear receptor binding sites, NR1 and NR2. Consistent with the finding that anti-retinoid X receptor (RXR) could supershift the NR1-nuclear protein complex, DNA affinity chromatography with NR1 oligonucleotides enriched the nuclear orphan receptor RXR from the hepatic nuclear extracts of phenobarbital-treated mice. In addition to RXR, the nuclear orphan receptor CAR was present in the same enriched fraction. In the phenobarbital-treated mice, the binding of both CAR and RXR was rapidly increased before the induction of CYP2B10 mRNA. In vitro-translated CAR bound to NR1, but only in the presence of similarly prepared RXR. PBREM was synergistically activated by transfection of CAR and RXR in HepG2 and HEK293 cells when the NR1 site was functional. A CAR-RXR heterodimer has thus been characterized as a trans-acting factor for the phenobarbital-inducible Cyp2b10 gene.

MeSH terms

Amino Acid Sequence
Animals
Aryl Hydrocarbon Hydroxylases*
Binding Sites
Cells, Cultured
Constitutive Androstane Receptor
Cytochrome P-450 Enzyme System / genetics*
Cytochrome P450 Family 2
Dimerization
Enhancer Elements, Genetic*
Gene Expression Regulation* / drug effects
Humans
Male
Mice
Mice, Inbred C57BL
Molecular Sequence Data
Phenobarbital / pharmacology
Receptors, Cytoplasmic and Nuclear / genetics
Receptors, Cytoplasmic and Nuclear / metabolism*
Receptors, Retinoic Acid / metabolism*
Retinoid X Receptors
Steroid Hydroxylases*
Time Factors
Trans-Activators / genetics
Trans-Activators / metabolism*
Transcription Factors / metabolism*
Tumor Cells, Cultured

Substances

Constitutive Androstane Receptor
Receptors, Cytoplasmic and Nuclear
Receptors, Retinoic Acid
Retinoid X Receptors
Trans-Activators
Transcription Factors
Cytochrome P-450 Enzyme System
Steroid Hydroxylases
Aryl Hydrocarbon Hydroxylases
Cyp2b10 protein, mouse
Cytochrome P450 Family 2
Phenobarbital