New Recombinant Protein Expression and tagging System based on Programmed -1 Ribosomal Frameshifting

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So-young Park, Se Jong Han, Xu Zheng, Sang Jun Sim & Yang-Gyun Kim

Sungkyunkwan University, South Korea

For rapid and accurate quantitation of recombinant proteins during expression and after purification, without a large metabolic burden on host cells, we introduce a new tagging strategy that expresses both target proteins and limitedly tagged target proteins together in a single cell at a constant ratio by utilizing cis-elements of the programmed -1 ribosomal frameshifting (-1RFS) as an embedded device. The -1RFS is an alternative reading mechanism that composed of two relatively small RNA sequences, a slippery sequence and a downstream RNA secondary structure. This unusual translational mechanism effectively controls protein expression in many viruses. In this study, when a target gene is fused to the green fluorescent protein (GFP) gene with a -1RFS signal implanted in between, the unfused target and the target-GFP fusion proteins are expressed at a fixed ratio. The expression ratio between these two protein products is easily adjustable simply by changing ­1RFS signals. Our result demonstrates that this limited-tagging system was useful for the real-time monitoring of protein expression when optimizing expression condition for a new protein, and in monitoring large-scale bioprocesses. Thus, this new tagging method could open to a variety of applications. For example, this strategy allows direct measure of the quantity of a protein on a chip surface and easy application to proteome-wide study of gene products. This work was supported by the National Research Foundation (NRF) grant (grant no. 2012R1A1A2007721).