Class 2 CRISPR–Cas RNA-guided endonucleases: Swiss Army knives of genome editing

Abstract

CRISPR–Cas is a bacterial defense system against phage infection and nucleic acid invasion. Class 2 type II CRISPR–Cas9 has also been widely used for genome engineering. Here, we review novel insights into the CRISPR class 2 type V enzymes, specifically Cpf1 and C2c1, which display different DNA-recognition and cleavage characteristics than those of Cas9, the best-characterized member of class 2. Recent structures of these ribonucleoprotein complexes that capture several stages of the endonuclease reaction have provided molecular details of recognition, unzipping and cleavage of the target DNA, allowing their comparison with Cas9. A detailed understanding of these mechanisms is crucial for improving these genome engineering tools and expanding the genomic space that can be targeted.

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Figure 1: Overview of the structural organization of class 2 members of the CRISPR–Cas system.
Figure 2: PAM-dependent target-DNA recognition.
Figure 3: Conformational rearrangements upon target-DNA recognition by class 2 members of CRISPR–Cas.
Figure 4: Detailed view of the conformational changes of the REC lobe and septum upon R-loop formation.
Figure 5: Catalytic insights of the class 2 ternary complexes.

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Acknowledgements

The Novo Nordisk Foundation Center for Protein Research is financially supported by the Novo Nordisk Foundation (Grant NNF14CC0001). This work was also supported by a grant from the Danish Cancer Society to G.M. We thank the Swiss Light Source (PSI, Switzerland) and the Computerome, the Danish National Computer for Life Sciences, for supporting our research.

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Correspondence to Stefano Stella or Guillermo Montoya.

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Stella, S., Alcón, P. & Montoya, G. Class 2 CRISPR–Cas RNA-guided endonucleases: Swiss Army knives of genome editing. Nat Struct Mol Biol 24, 882–892 (2017). https://doi.org/10.1038/nsmb.3486

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