Harnessing tRNA for Processing Ability and Promoter Activity.

Transfer RNA (tRNA) and their associated production and processing machinery can be coopted as a versatile tool for the production of guide RNAs (gRNAs) for Cas9-based genome engineering. Using different tRNA variants enables the production of gRNAs at a variety of steady state levels. Furthermore, engineered tRNAs can be used to process gRNAs from Pol-II transcripts, thus enabling spatial/temporal control of gRNA expression. Here we describe the design, cloning, and testing of tRNA scaffolds for both Pol-III-driven expression of different levels of gRNAs, and for processing gRNAs from Pol-II transcripts.