Cutting it close: CRISPR-associated endoribonuclease structure and function

Trends Biochem Sci. 2015 Jan;40(1):58-66. doi: 10.1016/j.tibs.2014.10.007. Epub 2014 Nov 18.


Many bacteria and archaea possess an adaptive immune system consisting of repetitive genetic elements known as clustered regularly interspaced short palindromic repeats (CRISPRs) and CRISPR-associated (Cas) proteins. Similar to RNAi pathways in eukaryotes, CRISPR-Cas systems require small RNAs for sequence-specific detection and degradation of complementary nucleic acids. Cas5 and Cas6 enzymes have evolved to specifically recognize and process CRISPR-derived transcripts into functional small RNAs used as guides by interference complexes. Our detailed understanding of these proteins has led to the development of several useful Cas6-based biotechnological methods. Here, we review the structures, functions, mechanisms, and applications of the enzymes responsible for CRISPR RNA (crRNA) processing, highlighting a fascinating family of endonucleases with exquisite RNA recognition and cleavage activities.

Keywords: CRISPR–Cas; Cas5; Cas6; crRNA; endoribonuclease; structure and function.

Publication types

  • Review

MeSH terms

  • Bacteria / genetics
  • Bacteria / immunology
  • CRISPR-Associated Proteins / chemistry*
  • CRISPR-Associated Proteins / genetics
  • CRISPR-Associated Proteins / metabolism
  • CRISPR-Cas Systems / genetics*
  • Endoribonucleases / chemistry*
  • Endoribonucleases / genetics
  • Endoribonucleases / metabolism
  • Protein Conformation
  • Protein Folding
  • RNA / chemistry
  • RNA / genetics
  • RNA Interference
  • Structure-Activity Relationship*
  • Substrate Specificity


  • CRISPR-Associated Proteins
  • RNA
  • Endoribonucleases