CRISPR DNA elements controlling site-specific spacer integration and proper repeat length by a Type II CRISPR-Cas system.

ABSTRACT: CRISPR-Cas systems provide heritable immunity against viruses by capturing short invader DNA sequences, termed spacers, and incorporating them into the CRISPR loci of the prokaryotic host genome. Here, we investigate DNA elements that control accurate spacer uptake in the type II-A CRISPR locus of Streptococcus thermophilus. We determined that purified Cas1 and Cas2 proteins catalyze spacer integration with high specificity for CRISPR repeat junctions. We show that 10 bp of the CRISPR leader sequence is critical for stimulating polarized integration preferentially at the repeat proximal to the leader. Spacer integration proceeds through a two-step transesterification reaction where the 3' hydroxyl groups of the spacer target both repeat borders on opposite strands. The leader-proximal end

SUBMITTER: Kim JG 

PROVIDER: S-EPMC6895254 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature