Light‐Activated Gene Expression System Using a Caging‐Group‐Free Photoactivatable Dye

Abstract Optical regulation of transcription using chemical compounds is an effective strategy to manipulate gene expression spatiotemporally. Conventional caging approaches with photoremovable protecting groups may require intense UV‐light exposure and release potentially toxic byproducts. To address these problems, here we developed a light‐mediated transcriptional regulation system by combining a caging‐group‐free photoactivatable dye PaX 560 and a multidrug‐binding transcriptional regulator QacR. The cationic dye generated from PaX 560 through traceless photoconversion bound QacR and reduced its repressor function, resulting in transcriptional activation. Importantly, this system allowed transcriptional activation with a large dynamic range under mild visible light exposure and simultaneous detection of the state of the photoactivated effector. This module was integrated into the T7 RNA polymerase expression system to demonstrate light‐activated transcription in vitro and in living cells.