Programmable multistep CRISPR gene activation via control of RNA polymerase III termination.

Although genomes encode instructions for mammalian cell differentiation with rich syntactic relationships, existing methods for genetically programming cells have only modest capabilities for stepwise gene regulation. Here, we develop a sequential genetic system that transcriptionally activates endogenous genes in a preprogrammed, stepwise manner. This system uses the removal of an RNA polymerase III termination sequence to trigger both the transcriptional activation and DNA endonuclease activities of a Cas9-VPR protein, driving progression through a cascade of gene activation events. The system's functionality in human cells, including iPSCs, enables the development of a path for cellular programming by controlling the sequential order of gene activation to influence cellular states.