The human
cytochrome P450 2J2 (
CYP2J2) generates cytoprotective epoxyeicosatrienoic
acids from
arachidonic acid. Expression of
CYP2J2 is decreased in
hypoxia, and the resultant decrease in CYP2J2-derived epoxyeicosanoids may contribute to the pathogenesis of cardiac ischaemia. Recent studies have indicated that
AP-1 (activator protein-1) regulates
CYP2J2 expression in normoxia and
hypoxia. Down-regulation of
CYP2J2 in hypoxic HepG2 cells was closely associated with the up-regulation of c-fos and transient transfection analysis demonstrated that c-Fos abolishes the activation of
CYP2J2 by the
AP-1 protein c-Jun. Deletion of the region between nt -122 and -50 upstream of the
start codon in
CYP2J2 prevented c-Jun transactivation. In this study we demonstrate that the sequence at -105/-95 is a major regulatory
element that binds c-Jun and has a prominent role in
CYP2J2 gene transactivation. Mutagenesis of both the -105/-95 region and the previously identified
element at -56/-63 was required for complete loss of transactivation by c-Jun; separate mutagenesis of the -105/-95
element or, to a lesser extent, the -56/-63
element resulted in a partial loss of gene activation. In contrast to the behaviour of the -56/-63
element, c-Jun homodimers and c-Fos/c-Jun heterodimers bound to the -105/-95
element. These findings demonstrate that the c-Jun-responsive module between -122 and -50 in the
CYP2J2 proximal promoter contains an atypical
AP-1 element at -105/-95 that has a major role in c-Jun transactivation and acts in conjunction with the -56/-63
element to regulate expression.