Harnessing type I CRISPR-Cas systems for genome engineering in human cells.

Type I CRISPR-Cas systems are the most abundant adaptive immune systems in bacteria and archaea. Target interference relies on a multi-subunit, RNA-guided complex called Cascade, which recruits a trans-acting helicase-nuclease, Cas3, for target degradation. Type I systems have rarely been used for eukaryotic genome engineering applications owing to the relative difficulty of heterologous expression of the multicomponent Cascade complex.

Mapping the genomic landscape of CRISPR-Cas9 cleavage.

RNA-guided CRISPR-Cas9 endonucleases are widely used for genome engineering, but our understanding of Cas9 specificity remains incomplete. Here, we developed a biochemical method (SITE-Seq), using Cas9 programmed with single-guide RNAs (sgRNAs), to identify the sequence of cut sites within genomic DNA. Cells edited with the same Cas9-sgRNA complexes are then assayed for mutations at each cut site using amplicon sequencing.