TFAP2A gene contains four alternative first exons which encode conserved protein sequences. (a) Schematic representation of TFAP2A 5' gene structure (exons 1 to 3). Exons are shown as rectangles, introns as horizontal lines, drawn in proportion to their actual length. Closed rectangles represent translated regions, open rectangles represent untranslated regions. Isoforms 1b and 1c are orthologous to the murine isoform 3  and ovine variant 6 , respectively. (b) TFAP2A protein sequences encoded by the four alternative first exons. Possible starting methionine residues are underlined. AP-2α isoform/variant 4 (as described in  and , respectively), generated by initiation of transcription upstream of exon 2, does not have a human paralog due to the presence of an in-frame stop codon upstream of exon 2. (c) Alignment of TFAP2A isoform 1c protein sequences in H. sapiens, D. rerio and X. tropicalis generated by ClustalW. Sequences for rhesus, mouse, dog and elephant are identical to the human sequence. * indicates an identical amino acid; : and . indicate conserved and semi-conserved substitutions, respectively. A conserved TATA-box is present 237 bp upsteam of the ATG. (d) Alignment of TFAP2A isoform 1b protein sequence to TFAP2B isoform 1b (EST: BM727695), TFAP2D (NM_172238.3) and TFAP2E (NM_178548.3) generated by ClustalW. Human sequences are shown.