Uncovering the distinct properties of a bacterial type I-E CRISPR activation system

Abstract

Synthetic gene regulators based upon CRISPR-Cas systems offer highly programmable technologies to control gene expression in bacteria. Bacterial CRISPR activators (CRISPRa) have been developed that use engineered type II CRISPR-dCas9 to localize transcription activation domains near promoter elements to activate transcription. However, several reports have demonstrated distance-dependent requirements and periodical activation patterns that overall limit the flexibility of these systems. Here, we demonstrate the potential of using an alternative type I-E CRISPR-Cas system to create a CRISPRa with distinct and expanded regulatory properties. We create the first bacterial CRISPRa system based upon a type I-E CRISPR-Cas, and demonstrate differences in the activation range of this system compared to type II CRISPRa systems. Furthermore, we characterize the distance-dependent activation patterns of type I-E CRISPRa to reveal a distinct and more frequent periodicity of activation.