Profiling of engineering hotspots identifies an allosteric CRISPR-Cas9 switch

A small-molecule-inducible Cas9 variant with very low background activity is identified by screening for sites that can tolerate domain insertions. The clustered, regularly interspaced, short palindromic repeats (CRISPR)-associated protein Cas9 from Streptococcus pyogenes is an RNA-guided DNA endonuclease with widespread utility for genome modification. However, the structural constraints limiting the engineering of Cas9 have not been...