Sequence Requirements for Cascade Function in a Type I-E CRISPR System: ChIP Library-seq. Sequence Requirements for Cascade Function in a Type I-E CRISPR System: ChIP Library-seq

We generated a collection of 13 plasmids, with each plasmid containing a variant of a CRISPR protospacer targeted by spacer 8 of the E. coli CRISPR-I array. We transformed the plasmids as a pool into delta cas3 E. coli cells expressing all other cas genes constitutively, with FLAG-tagged casA. We then used ChIP to enrich for CasA-bound protospacers. DNA surrounding the protospacers was PCR-amplified from input (pre-immunocrecipitation) and ChIP (post-immunoprecipitation) samples and sequenced.