Programmable DNA cleavage in vitro by Cas9

The ternary Cas9–crRNA–tracrRNA complex (Cas9t) of the Type II CRISPR (clustered regularly interspaced short palindromic repeats)–Cas (CRISPR-associated) system functions as an Mg2+-dependent RNA-directed DNA endonuclease that locates its DNA target guided by the crRNA (CRISPR RNA) in the tracrRNA–crRNA structure and introduces a double-strand break at a specific site in DNA. The simple modular organization of Cas9t, where specificity for the...