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CRISPR technologies and the search for the PAM-free nuclease

Nat Commun. 2021 Jan 22;12(1):555. doi: 10.1038/s41467-020-20633-y.

Abstract

The ever-expanding set of CRISPR technologies and their programmable RNA-guided nucleases exhibit remarkable flexibility in DNA targeting. However, this flexibility comes with an ever-present constraint: the requirement for a protospacer adjacent motif (PAM) flanking each target. While PAMs play an essential role in self/nonself discrimination by CRISPR-Cas immune systems, this constraint has launched a far-reaching expedition for nucleases with relaxed PAM requirements. Here, we review ongoing efforts toward realizing PAM-free nucleases through natural ortholog mining and protein engineering. We also address potential consequences of fully eliminating PAM recognition and instead propose an alternative nuclease repertoire covering all possible PAM sequences.

Publication types

  • Research Support, N.I.H., Extramural
  • Review

MeSH terms

  • Binding Sites / genetics
  • CRISPR-Associated Protein 9 / classification
  • CRISPR-Associated Protein 9 / genetics
  • CRISPR-Associated Protein 9 / metabolism*
  • CRISPR-Cas Systems*
  • Gene Editing / methods*
  • Models, Genetic
  • Nucleotide Motifs*
  • Phylogeny
  • Protein Engineering / methods
  • RNA, Guide, CRISPR-Cas Systems / genetics
  • RNA, Guide, CRISPR-Cas Systems / metabolism*

Substances

  • RNA, Guide, CRISPR-Cas Systems
  • CRISPR-Associated Protein 9