Role of activator protein-1 in the down-regulation of the human CYP2J2 gene in hypoxia

Nicole Y. Marden, Eva Fiala-Beer, Shi Hua Xiang, Michael Murray

Research output: Contribution to journalArticlepeer-review

43 Scopus citations

Abstract

The cytochrome P450 (CYP) 2J2 arachidonic acid epoxygenase gene was down-regulated at a pre-translational level in human hepatoma-derived HepG2 cells incubated in a hypoxic environment; under these conditions, the expression of c-Jun and c-Fos mRNA and protein was increased. The 5′-upstream region of the CYP2J2 gene was isolated by amplification of a 2341 bp fragment and putative regulatory elements that resembled activator protein-1 (AP-1)-like sequences were identified. From transient transfection analysis, c-Jun was found to strongly activate a CYP2J2-luciferase reporter construct, but co-transfection with plasmids encoding c-Fos or c-Fos-related antigens, Fra-1 and -2, abrogated reporter activity. Using a series of deletion-reporter constructs, a c-Jun-responsive module was identified between bp - 152 and - 50 in CYP2J2: this region contained an AP-1-like element between bp - 56 and - 63. The capacity of this element to interact directly with c-Jun, but not c-Fos, was confirmed by electromobility-shift assay analysis. Mutagenesis of the - 56/ - 63 element abolished most, but not all, of the activation of CYP2J2 by c-Jun, thus implicating an additional site within the c-Jun-responsive region. The present results establish an important role for c-Jun in the control of CYP2J2 expression in liver cells. Activation of c-Fos expression by hypoxia promotes the formation of c-Jun/c-Fos heterodimers, which decrease the binding of c-Jun to the CYP2J2 upstream region, leading to gene down-regulation.

Original languageEnglish (US)
Pages (from-to)669-680
Number of pages12
JournalBiochemical Journal
Volume373
Issue number3
DOIs
StatePublished - Aug 1 2003

Keywords

  • Activator protein-1
  • Cytochrome P450
  • Human gene regulation
  • Hypoxia
  • Transcription

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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