Fig. 1

Schematic of alternative corepressor splicing compared to an evolutionary dendrogram. The abundance of each alternative-splice variant from each splice site analyzed is presented schematically as a red bar, with its thickness proportional to the percent of the total splice variants expressed from that site (= 100%, see key). Absence of a bar indicates “not detected” (< 2% of total expression at each splice site); see the Limitations section and Additional file 1 for an expanded discussion of the sensitivity and accuracy of the RT-PCR technique). The species/sources newly analyzed for the current study (Alligator, Alligator mississippiensis; Bat, Eidolon helvum; Cat, Felis silvestris catus; Chicken, Gallus gallus domesticus; Dog, Canis lupus familiaris; Elephant, Loxodonta africana; Horse, Equus ferus caballus, Human, Homo sapien; Mouse, Mus musculus; Pig, Sus scrofa domesticus; Rabbit, Oryctolagus cuniculus; Rat, Rattus norvegicus; Rhesus, Macaca mulatta) are listed in black text and represent assays of RNA populations isolated from peripheral blood. Several additional species analyzed in a prior study [23], in grey text, are presented for comparison purposes and represent assays of RNA from non-hematological samples (Sheep, Ovis aries adult liver; Opossum, Monodelphis domestica adult liver; Turtle, Trachemys scripta adult liver; Frog, Xenopus laevis stage 45; Zebrafish, Danio rerio stage 84 h). The evolutionary relationships of the species are presented as a dendrogram with an estimate of divergence times (in millions of years, Mrys) presented below; please note break in time line. For ease of comparisons with other publications our prior nomenclature (NCoR and SMRT [23]) has been changed in the current manuscript to NCoR-1 and NCoR-2, respectively. The exon numbering system is that employed in our prior study [23]