Human Leukotriene B 4 Ω- Hydroxylase ( CYP4F3 ) Gene: Molecular Cloning and Chromosomal Localization

Abstract

Leukotriene B₄ (LTB₄) Ω-hydroxylase catalyzes the conversion of LTB₄ into a biologically less active product, 20-hydroxy-LTB₄. In a preceding paper (Kikuta et al., 1993), we showed human polymorphonuclear leukocyte (PMN) LTB₄ Ω-hydroxylase to be a novel form of cytochrome P450, designated CYP4F3, on the basis of its cDNA cloning and expression in yeast cells. Here, we have isolated the gene encoding CYP4F3 and determined its genomic organization and chromosomal localization. The CYP4F3 gene contained 13 exons and spanned approximately 22.2 kb. The cDNA of CYP4F3 contained 5050 nucleotides excluding the poly(A) tail. The translation initiation codon (ATG) was present in exon II. Primer extension and SI mapping analyses indicated that the transcription initiation site is 49 nucleotides upstream from the 3′ end of exon I, and no other initiation sites were detected. A TATA-box-like sequence (TACAT) and 120-b GC-rich sequence were observed just before transcription initiation site. Several putative regulating elements recognized by the GATA family, MZF-1, CACCC binding protein, and C/EBP, were identified in its 5′ flanking region. Genomic DNA screening for CYP4F3 and Southern blot analysis suggested the existence of other CYP4F genes in addition to CYP4F3 and CYP4F2 in the human genome. Fluorescence in situ hybridization demonstrated that the CYP4F3 gene is located at 19pl3.2.