Quantification of durable CRISPR-based gene silencing activity

Development of CRISPR-based technologies for regulating gene expression stands to provide novel methods for the study and engineering of biological behavior. New tools capable of inducing long-lasting changes in gene expression will increase the utility of these techniques, providing durable effects from one-time doses of reagents. We describe here a reporter system for quantifying the ability of CRISPR-based effectors to induce stable gene repression. We observe a continuous gradation of the ability of these effectors to silence gene expression, depending on the domain composition and configuration. We also report the creation of a single CRISPR protein capable of producing durable gene silencing. This assay should allow for the continued development of enhanced gene repression tools which will be useful in a wide array of biological research and engineering applications.