Cas9-dna targeting unit chimeras

TLDR: In this article, a Cas9-DTU fusion protein was proposed to facilitate single-site nuclease gene editing precision within a human genome. But, this method is not suitable for single-genomic-site accuracy.

Abstract: The present invention provides a Cas9 platform to facilitate single-site nuclease gene editing precision within a human genome. For example, a Cas9 nuclease/DN A- targeting unit (Cas9-DTU) fusion protein precisely delivers a Cas9/sgRNA complex to a specific target site within the genome for subsequent sgRNA-dependent cleavage of an adjacent target sequence. Alternatively, attenuating Cas9 binding using mutations to the a protospacer adjacent motif (PAM) recognition domain makes Cas9 target site recognition dependent on the associated DTU, all while retaining Cas9's sgRNA-mediated DNA cleavage fidelity. Cas9-DTU fusion proteins have improved target site binding precision, greater nuclease activity, and a broader sequence targeting range than standard Cas9 systems. Existing Cas9 or sgRNA variants (e.g., truncated sgRNAs (tru-gRNAs), nickases and Fokl fusions) are compatible with these improvements to further reduce off-target cleavage. A robust, broadly applicable strategy is disclosed to impart Cas9 genome-editing systems with the single-genomic-site accuracy needed for safe, effective clinical application.