Fig. 1.

MAOA RNA of Tg8 mice (A) Representation of the Tg8 gene encoding MAOA between exons 1 and 8 (the gene for MAOA probably has 15 exons) and structure of the four species of MAOA RNA detected by RT-PCR. The species containing IFN-β sequences (an exon of 199 bp) results from splicing events between legitimate MAOA splice sites and cryptic IFN-β splice sites (SA and SD, acceptor and donor sites present in antisense IFN-β RNA). (B) Sequence of SA and SD, and sequence of MAOA exon 2 acceptor splice site. The MAOA exon 2 acceptor has a strong putative branch site sequence (TGTTAAC), as opposed to the cryptic acceptor SA. (C) C3H MAOA sequences obtained by RT-PCR between exons and 8. The Tg8 RNA splice between exons 1 and 4 causes a reading frame shift, and the IFN-β exon of the hybrid RNA species does not restore the normal reading frame. Internal initiation of translation may occur at ACAATG within exon 4.