Fig. 2

Mosaic conservation of the exon 1A in mammal evolution. a Examination of the exon 1A region in mammals. The yellow box represents the exon 1A in several mammal species [details in Additional file 6: dataset S6]. In human, two putative ATG could initiate the translation of a protein. For all species, these ATG are indicated as ATG1 and ATG2 when conserved. When not, the corresponding mutated codon is shown. The conservation of the promoter, the splice donor site and the frame were also studied and are indicated with symbols. The isoform-A transcript was detected by RT-PCR in human, guinea pig (Cavia) and wallaby (Macropus) or identified by BLAST against EST databases in macaca and cow (Bos). Species that are considered to have lost the ability to produce isoform A are shown in red. b In vitro translation experiments. The exon 1A of Homo [43], Homo mutated for the first ATG (2), Homo mutated for the second ATG [44], Homo mutated for both ATG [43] Cavia (5), Equus (6), Vicugnia (7) were cloned upstream the Renilla gene to test by in vitro translation their ability to produce a protein from the first exon with different ATG 1 and 2 context. The asterisk shows two faint bands that are the result of low efficiency initiation at a downstream non-specific ATG. The dark red arrow points out the faint band initiated by an alternative AAG codon for the human double mutant