Structure of an ovine CYP11B1 gene

Glucocorticoids play an important role in the normal development and proliferation of cells, and are also involved in inflammatory responses. The level of active glucocorticoids in the body is controlled in part by the enzyme CYP11B1, which catalyses the final step of its biosynthesis. In this report, we have completely characterised the ovine CYP11B1 gene using two overlapping clones isolated from an lambdaEMBL3 sheep liver genomic library. The gene comprised 9 exons and 8 introns, spanning over a region of 8.0 kb. Two ovine CYP11B1 transcripts, with molecular sizes of 1.9 and 4.0 kb, have also been isolated from the adrenal zona fasciculata region, which showed that 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 mapped using primer extension analysis. Three major start sites were identified at positions -5, -6 and -77 from the first ATG codon (Met), with two minor sites located at positions -306 and -413. When examined in context with the ovine CYP11B1 5' regulatory region, the results suggested that the ovine CYP11B1 gene contained two additional core promoters located further upstream of a proximal TATA box which could be utilised to produce mRNAs with alternative transcriptional start sites.