Compositions and methods for the expression of selenoproteins in eukaryotic cells

A recombinant nucleic acid construct comprising a sequence that encodes a chimeric eukaryotic selenocysteine insertion sequence (SECIS) element that is operably linked to both a heterologous expression control sequence and a heterologous sequence comprising a site for operable insertion of a heterologous nucleic acid sequence that encodes a heterologous polypeptide, wherein a native 5′ proximal 5′-GGAN-3′ quartet sequence in a non-canonical SECIS element is replaced by a non-native 5′ proximal 5′-UGAN-3′ quartet sequence to provide said chimeric SECIS element.

A method for obtaining a selenoprotein comprising the steps of:

• (a) culturing a cell comprising a recombinant nucleic acid construct under conditions permitting expression of a selenoprotein encoded by said recombinant nucleic acid construct, said recombinant nucleic acid construct comprising a sequence that encodes a chimeric selenocysteine insertion sequence (SECIS) element that is operably linked to both a heterologous expression control sequence and a heterologous sequence that encodes a heterologous polypeptide and contains at least one UGA codon, wherein a native 5′ proximal 5′-GGAN-3′ quartet sequence in a non-canonical SECIS element is replaced by a non-native 5′ proximal 5′-UGAN-3′ quartet sequence to provide said chimeric SECIS element;
• and
• (b) recovering said selenoprotein from said cell of step (a) or from a cell culture medium of step (a), thereby obtaining a selenoprotein.

An isolated nucleic acid comprising a heterologous coding sequence operably linked to a sequence that encodes a eukaryotic selenocysteine insertion sequence (SECIS) element, said SECIS element comprising a 5′ proximal 5′-GGAN-3′ quartet sequence and wherein said nucleic acid sequence comprises at least one UAG codon.

An isolated nucleic acid comprising a heterologous coding sequence operably linked to a sequence that encodes a chimeric eukaryotic selenocysteine insertion sequence (SECIS) element, wherein a native 5′ proximal 5′-GGAN-3′ quartet sequence in a non-canonical SECIS element is replaced by a non-native 5′ proximal 5′-UGAN-3′ quartet sequence to provide said chimeric SECIS element wherein said nucleic acid sequence comprises at least one UAG codon.