Alternative transcripts and N-termini produced by transcription from proximal and distal promoters of vertebrate runx genes. (A) Diagram of alternative transcripts from distal (P1) and proximal (P2) promoters in vertebrate Runx genes. Solid lines represent untranslated regions of exons, while dashed lines represent introns. TrRunx1 distal transcript is theoretical and based on its similarities to other distal transcripts (i.e., its open reading frame begins with a sequence encoding MASNS), location (~14 kb from proximal transcript) and size (19 aa). TrRunx2 and TrRunx3 transcripts from P1 were derived from similarities to MmRunx2 and Danio rerio runtb, respectively. TrRunx2 was recently published . M. musculus distal transcripts were gathered from Genebank entries and verified with publications (see Supplemental Table 1). Note: Unlike all of the other vertebrate Runx genes in our collection, TrRunx1 transcript from P2 has a small exon (encoding 9 amino acids) followed by a 1 kb intron (see also B, below, and Supplemental Figure 1). This small exon splices into the same location within the downstream coding sequence as does the exon from the distal transcript. (B) Alternative N-terminal amino acid sequences of various vertebrate Runx genes analysed in our survey. N-termini from the distal promoters are shown in green, while the N-termini from the proximal promoters are shown in red. The aspartate or glutamate to which the N-terminal sequences from the distal promoter are joined are highlighted in yellow. The positions and nucleotides at the termini of introns are indicated in lower case.