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. Author manuscript; available in PMC: 2014 Oct 8.
Published in final edited form as: J Am Chem Soc. 2013 Aug 27;135(36):13433–13439. doi: 10.1021/ja4051026

Figure 1. The light-activated T7RNAp is expressed in mammalian cells through site-specific incorporation of a photocaged lysine (PCK) into its active site in response to an amber stop codon (TAG) via an engineered tRNA synthetase (PCKRS) that misacylates an amber-suppressor tRNA (PylT) with PCK.

Figure 1

The caged T7RNAp is completely inactive until irradiation with 365 nm UV light induces decaging and activation of T7-driven transcription. Depending on the function of the transcribed RNA, light-induced protein expression from mRNA or light-induced gene silencing via RNA interference from shRNA is achieved.