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Nuclear receptor CAR requires early growth response 1 to activate the human cytochrome P450 2B6 gene

Kaoru Inoue1, Masahiko Negishi

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

The Journal of Biological Chemistry
|February 28, 2008
PubMed

Insights

The constitutive active/androstane receptor (CAR) requires early growth response 1 (EGR1) to activate the CYP2B6 gene, which metabolizes drugs. EGR1 links cellular signals with CAR

Area of Science:

  • Pharmacology
  • Molecular Biology
  • Genetics

Background:

  • The constitutive active/androstane receptor (CAR) is a key drug-sensing transcription factor regulating hepatic drug-metabolizing enzymes.
  • The human CYP2B6 gene encodes a crucial enzyme involved in metabolizing common therapeutics and activating prodrugs.
  • Understanding CAR's regulatory mechanisms is vital for drug metabolism and efficacy.

Purpose of the Study:

  • To elucidate the novel regulatory mechanism of CAR-mediated activation of the human CYP2B6 gene.
  • To investigate the role of the signal molecule early growth response 1 (EGR1) in CYP2B6 gene activation.
  • To determine the synergistic requirements for CAR to activate CYP2B6 gene expression.

Main Methods:

  • Characterization of gene regulation using molecular biology techniques.
  • Analysis of transcription factor binding to promoter and enhancer elements.
  • Investigating protein-protein interactions and signaling pathways.

Main Results:

  • CAR directly binds to the distal enhancer of the CYP2B6 promoter, but this binding alone is insufficient for activation.
  • Early growth response 1 (EGR1) is essential for CAR to activate the CYP2B6 promoter.
  • EGR1, upon protein kinase C stimulation, binds the proximal promoter and coordinates with HNF4alpha and CAR at the distal enhancer.

Conclusions:

  • CAR-mediated activation of the human CYP2B6 gene requires a synergistic interplay between drug sensing and cellular signaling pathways.
  • EGR1 acts as a critical mediator, linking cellular signals to CAR's function at the CYP2B6 promoter.
  • Both CAR and EGR1, along with HNF4alpha, are necessary for robust CYP2B6 gene activation.

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