NOVEL AROMATASE TRANSCRIPTS FROM BOVINE PLACENTA CONTAIN REPEATED SEQUENCE MOTIFS

Aromatase cytochrome P-450 (Aro) is the major enzyme of estrogen biosy nthesis. The aim of the present investigation was the isolation and co mparative sequence analysis of the bovine aromatase cytochrome P-450 t ranscript (bCyp19) from a placental lambda gt10 cDNA library. From thr ee overlapping clones, a total sequence of 5180 bp could be derived, i ncluding two polyadenylation sites and signals located next to each ot her. As found in other species, the open reading frame (ORF) comprises 1509 bp and shows 87, 78 and 78% sequence homology to the coding area s of the human, rat and mouse genes, respectively. The 3'-untranslated region (UTR) of the bovine transcript is about 2-kb longer than that of the human gene (hCYP19). It contains homologous retroposon elements of the bovidae dimer family (BDF) at two different positions, and end s with a sequence motif which also occurs repeatedly within the bovine genome. The 5'-UTR isolated from placenta includes a new sequence ups tream from exon II that was not found in cattle or other species so fa r. We conclude from our data that (i) as found in other species, bCyp1 9 is likely to be transcribed into different mRNA species, (ii) the bo vine 3'-UTR was the target for multiple insertions of repeated sequenc e motifs, (iii) the unusual length of the bCyp19 transcript is mainly due to the long 3'-UTR, (iv) it includes sequences which are found in humans only on the genomic level, conceivably due to mutational inacti vation of a primordial polyadenylation signal (PAS) and (v) the recent ly used, functional PAS is contributed by a downstream bovine repeat e lement.