Selenoproteins were chosen according two fundamental criteria:
We established these conditions before selecting any of the selenoproteins to study. Even though we tried to follow both conditions, the limited list of available selenoproteins and their specific sequences determined our choice in the case of selenoprotein V (one SNP in an intron).
In selenoprotein V, only one SNP was found. It is located within an intron.
In selenoproteins K and H, the SNPs found in the 3'UTR were located within the sequence corresponding to the 100 nucleotides of the secis element, but did not match any of the critical positions. Therefore, the structure was not affected.
Although each selenoprotein has a characteristic secis element, most of them show high conservation on some sequence positions that are esential to the function of the element.
This critical positions enable the secis element to generate a loop in the mRNA which is essential to the incorporation of selenocysteine. As mutations in these positions are limitant to the formation of such loop, these positions are highly restricted by selection.
The high conservation found in these specific sequences drive us to think about how functionally relevant is the selective pressure towards its conservation, due to the fact that the changes are penalized with an unviable selenoprotein.
We stressed the importance of the study of the Secis element sequences among the different selenoproteins to determine if common patterns of changes are generated in the different species appart from the general conservations of selenoproteins through evolution.
Thus, a change in these nucleotides would produce a defective bracket, unless presence of complementary nucleotides.
| BACK | MAIN | NEXT |