Metabolite-responsive scaffold RNAs for dynamic CRISPR transcriptional regulation.

CRISPR activation is a powerful tool to upregulate a vast array of genes in many different contexts. However, there are few dynamic CRISPR transcriptional programs, which limit its usage in the creation of living biosensors, self-regulating microbial factories, or conditional therapeutics. Here, we address this limitation by embedding a molecular switch directly into a guide RNA to create a combined sensor-actuator called a metabolite-responsive scaffold RNA (MR-scRNA). We demonstrate the regulatory potential for MR-scRNAs by conditionally activating genes in three different kingdoms of life. We create MR-scRNAs responsive to two distinct metabolites, theophylline and tryptophan, by swapping the molecular switch used. MR-scRNAs respond quickly in a dose-dependent manner specifically to their target metabolite and enhance biochemical production when used as a dynamic regulator of pathway enzyme expression. The broad functionality and ease of design of the MR-scRNAs offer a promising tool for dynamic cellular regulation.