Identification and characterization of transcriptional regulatory elements of the human aromatase cytochrome P450 gene (CYP19)

Aromatase cytochrome P450, a member of the cytochrome P450 gene super family, catalyzes conversion of androgens to estrogens in a form of an enzyme-complex with NADPH-cytochrome P450 reductase. Transcription of the aromatase cytochrome P450 gene (CYP19) is regulated in part by tissue-specific promoters coupled with alternative splicing mechanisms. The transcription in human placenta is governed by a promoter activity of the 5' flanking region of exon I.1, which is mapped more than 40 kb upstream from the translational start codon observed in exon II. Transient expression analyses with chimeric constructs containing the 5' flanking sequences linked to the bacterial chloramphenicol acetyltransferase (CAT) gene in human BeWo choriocarcinoma cells localized a cell-type specific enhancer element between -242 and -166 relative to the major cap site. DNase I footprinting and transient expression analyses of the enhancer element indicate that it consists of two sub-elements and that both sub-elements are necessary for the maximum enhancement of the transcription. In addition to the enhancer element, a cis-acting element important for transcriptional enhancement of the gene in response to 12-O-tetradecanoylphorbol 13-acetate in BeWo cells is localized between -2141 and -2115. A nuclear factor binding to the element is identified as NF-IL6 (also termed as LAP and C/EBP β). Transient expression analyses using the CAT constructs containing the NF-IL6 binding sites establish involvement of the factor in transcriptional regulation of CYP19.