ABSTRACT

Selenium is an essential micronutrient. Its role has been attributed largely to its presence in selenoproteins, as part of selenocysteine (Sec, U), the 21st amino acid. The incorporation of selenocysteine into a selenoprotein requires a specific mechanism to decode the UGA codon, which normally signals translation termination, into Sec. This codon duality makes selenoprotein annotation challenging. The aim of this project was to search for selenoproteins and selenoprotein homologues in the genome of Saimiri boliviensis (Bolivian squirrel monkey). Because the synthesis of selenoproteins requires a specific machinery, we also searched for the proteins of the machinery. The fact that Saimiri boliviensis and Homo sapiens present phylogenetic proximity let us use gene prediction based on homology to human proteins, which are already annotated. We first ran tblastn to identify genomic regions with similarity to the human sequences. The genomic regions where hits were obtained were used for gene prediction with exonerate and GeneWise. T-Coffee was then used to align the predictions with their respective queries. Since the incorporation of selenocysteine into a protein requires a SECIS element, we used SECISearch to predict SECIS elements, together with blastn to find regions homologous to the annotated human SECIS elements. Finally, Selenoprofiles was used to complement our analysis. Our predictions suggest that Saimiri boliviensis has a selenoproteome highly similar to humans. The most notable difference is that GPx6 is predicted to contain cysteine instead of selenocysteine in Saimiri boliviensis. Besides, the region encoding GPx1 is not properly sequenced so the presence of this protein will require further analysis. We also predicted that Saimiri boliviensis has the proteins required for selenoprotein synthesis. As expected, we could not identify any of the non-human selenoproteins.