Structure of an ovine CYP11B1 gene

Glucocorticoids play an important role in the normal development and prolif eration of cells, and are also involved in inflammatory responses. The leve l of active glucocorticoids in the body is controlled in part by the enzyme CYP11B1, which catalyses the final step of its biosynthesis. In this repor t, we have completely characterised the ovine CYP11B1 gene using two overla pping clones isolated from an lambda EMBL3 sheep liver genomic library. The gene comprised 9 exons and 8 introns, spanning over a region of 8.0 kb. Tw o ovine CYP11B1 transcripts, with molecular sizes of 1.9 and 4.0 kb, have a lso been isolated from the adrenal zona fasciculata region, which showed th at they arose from the usage of the two polyadenylation sites situated 2.1 kb apart in exon 9. The transcriptional start sites of the gene has been ma pped using primer extension analysis. Three major start sites were identifi ed at positions -5, -6 and -77 from the first ATG codon (Met), with two min or sites located at positions -306 and -413. When examined in context with the ovine CYP11B1 5' regulatory region, the results suggested that the ovin e CYP11B1 gene contained two additional core promoters located further upst ream of a proximal TATA box which could be utilised to produce mRNAs with a lternative transcriptional start sites.