4p6i

Publication Abstract from PubMed

The initial stage of CRISPR-Cas immunity involves the integration of foreign DNA spacer segments into the host genomic CRISPR locus. The nucleases Cas1 and Cas2 are the only proteins conserved among all CRISPR-Cas systems, yet the molecular functions of these proteins during immunity are unknown. Here we show that Cas1 and Cas2 from Escherichia coli form a stable complex that is essential for spacer acquisition and determine the 2.3-A-resolution crystal structure of the Cas1-Cas2 complex. Mutations that perturb Cas1-Cas2 complex formation disrupt CRISPR DNA recognition and spacer acquisition in vivo. Active site mutants of Cas2, unlike those of Cas1, can still acquire new spacers, thus indicating a nonenzymatic role of Cas2 during immunity. These results reveal the universal roles of Cas1 and Cas2 and suggest a mechanism by which Cas1-Cas2 complexes specify sites of CRISPR spacer integration.

Cas1-Cas2 complex formation mediates spacer acquisition during CRISPR-Cas adaptive immunity.,Nunez JK, Kranzusch PJ, Noeske J, Wright AV, Davies CW, Doudna JA Nat Struct Mol Biol. 2014 May 4. doi: 10.1038/nsmb.2820. PMID:24793649^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.