Selenoproteins are proteins that contain a rare amino acid called selenocysteine (Sec) and is represented by a “U” character. Sec is encoded by the UGA codon, which normally signals translation termination. Moreover, another requisite to be a selenoprotein is to contain in the 3’UTR region a SECIS sequence, which is a conserved stem-loop structure designated as Sec Insertion Sequence element. This SECIS element is necessary for the recognition of UGA as a selenocysteine codon, rather than as a STOP signal.
The aim of this study was to find the selenoproteins present in Mus spicilegus, whose selenoproteome has never been studied before because its genome has been sequenced recently. We managed to annotate Mus spicilegus’s genome by the use of bioinformatic tools such as tblastn, Exonerate, T-Coffee and Seblastian and through a semi-automatic program designed by our group. The alignment was performed with Mus musculus, the most related phylogenetic species with a well annotated selenoproteome. However, those selenoproteins that did not start with a methionine, were also compared with Homo sapiens.
After the alignment, a total of eighteen selenoproteins were found on Mus spicilegus and all of the seven machinery proteins analysed were also present. However, just one of the machinery proteins was found to be a selenoprotein. In definitive, those machinery proteins are essential to have selenoproteins in the genome and that is why we found them conserved comparing to Mus musculus.