Light‐Activated Translation of Different mRNAs in Cells via Wavelength‐Dependent Photouncaging

The 5′ cap is a hallmark of eukaryotic mRNA involved in the initiation of translation. Its modification with a single photo‐cleavable group can bring translation of mRNA under the control of light. However, UV irradiation causes cell stress and downregulation of translation. Furthermore, complex processes often involve timed expression of more than one gene. The approach would thus greatly benefit from the ability to photo‐cleave by blue light and to control more than one mRNA at a time. We report the synthesis of a 5′ cap modified with a 7‐(diethylamino)coumarin (CouCap) and adapted conditions for in vitro transcription. Translation of the resulting CouCap‐mRNA is muted in vitro and in mammalian cells, and can be initiated by irradiation with 450 nm. The native cap is restored and no non‐natural residues nor sequence alterations remain in the mRNA. Multiplexing for two different mRNAs was achieved by combining cap analogs with coumarin‐ and ortho‐nitrobenzyl‐based photo‐cleavable groups.