Test system for quantification of stop codon suppression by selenocysteine insertion in mammalian cell lines

A convenient test system was designed to investigate the efficiencies of selenocysteine inserting sequences (SECIS) responsible for the cotranslational incorporation of selenocysteine into selenoproteins of mammals. It comprises an expression vector in which the lacZ and luc genes are separated by an in-frame TGA stop codon. The coding regions are followed by a multicloning region allowing exchange of putative SECIS elements. Stop codon suppression associated with selenocysteine incorporation is readily estimated on the basis of relative luciferase activity measurements, thus providing a measure of SECIS efficiency.