Kinetics of dCas9 target search in Escherichia coli

Abstract

Flexible association comes at a price The CRISPR-Cas9 genome editing system is guided to its target DNA sequence by a small RNA that must search the genome to find its target site. To allow the guide RNA to bind, Cas9 must unwind the DNA at each location that it searches. Jones et al. used single-molecule fluorescence methods and bulk biochemistry to show that Cas9 takes 6 hours to find its target sequence, with each potential target bound for less than 30 ms. Overall, the CRISPR-Cas9 system pays for its flexible association mechanism with slow kinetics, but this can be overcome by using high concentrations of Cas9 and guide RNA. Science , this issue p. 1420