A tandem gene duplication followed by recruitment of a retrotransposon created the paralogous bucentaur gene (bcnt^p97) in the ancestral ruminant

Retrotransposable element-1 (RTE-1) is a class of long interspersed nucleotide elements that contain in its open reading frame an apurinic/apyrimidinic endonuclease domain (AP-END) and a reverse transcriptase domain. Ruminants have a clade-specific RTE-1 (BovB/RTE). The bovine bcnt gene (bucentaur or craniofacial developmental protein 1) has a duplicated paralog (bcnt^p97) in tandem that recruited an AP-END of BovB/RTE as a coding exon (RTE exon). We obtained sequence of the bcnt region from several animals and showed that other ruminants also have the bcnt^p97 with a conserved RTE exon while camels and pigs do not. Genomic Southern analysis showed that camels and pigs have multiple bcnt-related sequences but not BovB/RTE which bovines and lesser mouse deer have abundantly. These results indicate that the bcnt gene duplication followed by the creation of bcnt ^p97 including recruitment of the RTE exon occurred in the ancestral ruminant about 55 MYA. The indication of time frame is supported by a phylogenetic analysis. Taken together with a result of differential tissue expression of the two bcnt paralogs, we conclude that bcnt^p97 was created concurrently with the early radiation of BovB/RTE in an ancestral ruminant and then acquired a novel function.