Functional expression of angiotensinogen depends on splicing enhancers in exon 2

Angiotensinogen belongs to the family of serpins and is the only precursor of the potent cardiovascular peptide, angiotensin II, the main effector of the renin-angiotensin system. The gene coding for this protein carries an internal exon (exon 2), the length of which (859 bp) by far exceeds the mean length of internal exons in vertebrates (<300 bp). Here, we show that this essential exon is skipped in about 20% of all transcripts in liver, brain, and kidney of rats and mice. Deletion mutants of exon 2 revealed a 62 bp region located at its 5'-end which is important for its inclusion in the mature angiotensinogen mRNA in transfected COS7 cells. Using an artificial minigene, we defined sequences inside this region as exonic splicing enhancers. These data reveal a novel molecular mechanism important for the renin-angiotensin system with implications in the basic understanding and the therapeutical assessment of cardiovascular diseases.