Cloning and characterization of the rat cytochrome P450 4F5 (CYP4F5) gene

Cytochrome P450 4Fs are required for metabolizing arachidonic acid derivatives such as lipoxins, prostaglandins, hydroxyeicosatetraenoic acids and, most importantly, leukotriene B(4), an inflammatory mediator involved in leukocyte attraction and blood vessel permeability regulation. CYP4F5 is one of the rat 4F subfamily members expressed in liver, kidney and brain. To understand the mechanism of gene regulation of CYP4F5, genomic clones for CYP4F5 were isolated and characterized. The gene organization reveals that CYP4F5 gene spans 15.5 kb, and contains 13 exons ranging from 54 to 964 bp. The positions of intron-exon junctions are similar to those of human 4F genes. The transcription start site was determined by 5' rapid amplification of DNA complementary to RNA (cDNA) end-polymerase chain reaction, and is located 10 bp upstream of the first nucleotide of cDNA identified originally by Kawashima and Strobel (Biochem. Biophys. Res. Commun. 217 (1995) 1137), and results in 83 bp of 5' untranslated region. The 4 kb 5' flanking region was sequenced and analyzed using TRANSFAC program for potential transcription factor binding sites. No TATA box was observed, but a CCAAT box was identified, and one Sp1 site is located on each side of the CCAAT box. The elements likely for nuclear receptors retinoic acid receptor, retinoic acid X receptor, hepatocyte nuclear factor-3, glucocorticoid receptor, nuclear factor-kappaB and activator protein-1 were also found. However no binding site for peroxisome poliferator-activated receptor was present in the 4 kb region analyzed. Transfection of deletion constructs of the 5' flanking region of CYP4F5/luciferase reporter gene identified that the first 134 bp of flanking region contained essential promoter sequences for constitutive expression of the CYP4F5 gene. Two negative regulatory regions were also identified. These studies provide insight into the mechanism of CYP4F subfamily gene regulation.