Genetic code expansion in mammalian cells: A plasmid system comparison.

Genetic code expansion with unnatural amino acids (UAAs) has significantly broadened the chemical repertoire of proteins. Applications of this method in mammalian cells include probing of molecular interactions, conditional control of biological processes, and new strategies for therapeutics and vaccines. A number of methods have been developed for transient UAA mutagenesis in mammalian cells, each with unique features and advantages. All have in common a need to deliver genes encoding additional protein biosynthetic machinery (an orthogonal tRNA/tRNA synthetase pair) and a gene for the protein of interest. In this study, we present a comparative evaluation of select plasmid-based genetic code expansion systems and a detailed analysis of suppression efficiency with different UAAs and in different cell lines.