Multiple non-coding exons and alternative splicing in the mouse Mas protooncogene

• This is the most complete description of the Mas gene structure and regulation.
• The murine Mas gene contains 12 exons, 11 in the 5′ untranslated mRNA.
• There are 4 promoters and 2 polyadenylation signals, organ specific regulated.
• Alternative splicing and multiple promoter usage lead to at least 12 transcripts.
• We identified the most complex gene structure for a GPCR described so far.

The Mas protooncogene encodes a G protein-coupled receptor with the common seven transmembrane domains, expressed mainly in the testis and brain. We provided evidence that Mas is a functional angiotensin-(1–7) receptor and can interact with the angiotensin II type1 (AT1) receptor. The gene is transcriptionally regulated during development in the brain and testis, but its structure was unresolved. In this study we used 5′- and 3′-RACE, RT-PCR, and RNase-protection assays to elucidate the complete Mas gene structure and organization.We identified 12 exons in the mouse Mas gene with 11 in the 5′ untranslated mRNA, which can be alternatively spliced. We also showed that Mas transcription can start from 4 tissue-specific promoters, whereby testis-specific Mas mRNA is transcribed from two upstream promoters, and the expression of Mas in the brain starts from two downstream promoters. Alternative splicing and multiple promoter usage result in at least 12 Mas transcripts in which different 5′ untranslated regions are fused to a common coding sequence. Moreover, termination of Mas mRNA is regulated by two different polyadenylation signals. The gene spans approximately 27 kb, and the longest detected mRNA contains 2451 bp.Thus, our results characterize the Mas protooncogene as the gene with the most complex gene structure of all described members of the gene family coding for G protein-coupled receptors.