Aptamer‐Mediated Reversible Transactivation of Gene Expression by Light

The investigation and manipulation of cellular processes with subcellular resolution requires non‐invasive tools with spatiotemporal precision and reversibility. Building on the interaction of the photoreceptor PAL with an RNA aptamer, we describe a variation of the CRISPR/dCAS9 system for light‐controlled activation of gene expression. This platform significantly reduces the coding space required for genetic manipulation and provides a strong on‐switch with almost no residual activity in the dark. It adds to the current set of modular building blocks for synthetic biological circuit design and is broadly applicable.