Diagrammatic representation summarizing the three major classes of transcriptional units generated at the Kua–UEV locus. Transcription from the promoter located upstream from the first exon ofKua can eventually yield either a Kua-only transcript ending in K6 (Kua), or a Kua–UEV hybrid transcript. The maturation of the longer transcript is possible only after removal of the K6 exon, which contains signals for truncation of the primary transcript. Transcription from the promoter located upstream from the A exon yields UEV1A. (Black boxes) Kua exons; (light grey boxes) UEV “common domain” exons; (shaded box)UEV “A” exon; (open boxes) 5′ and 3′ UTRs; (filled circles and arrows) putative transcription initiation sites.
