Cas5d processes pre-crRNA and is a member of a larger family of CRISPR RNA endonucleases (original) (raw)

  1. Matthew J. Schellenberg1,4,
  2. Emily M. Gesner1,
  3. Jeffrey B. Bonanno2,
  4. J. Michael Sauder3,
  5. Stephen K. Burley3,
  6. Steven C. Almo2,3,
  7. Garima Mehta1 and
  8. Andrew M. MacMillan1,5
  9. 1Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
  10. 2New York SGX Research Center for Structural Genomics (NYSGXRC), Department of Physiology & Biophysics, Albert Einstein College of Medicine, Bronx, New York 10461, USA
  11. 3New York SGX Research Center for Structural Genomics (NYSGXRC), Eli Lilly and Company, Lilly Biotechnology Center, San Diego, California 92121, USA

Abstract

Small RNAs derived from clustered, regularly interspaced, short palindromic repeat (CRISPR) loci in bacteria and archaea are involved in an adaptable and heritable gene-silencing pathway. Resistance to invasive genetic material is conferred by the incorporation of short DNA sequences derived from this material into the genome as CRISPR spacer elements separated by short repeat sequences. Processing of long primary transcripts (pre-crRNAs) containing these repeats by a CRISPR-associated (Cas) RNA endonuclease generates the mature effector RNAs that target foreign nucleic acid for degradation. Here we describe functional studies of a Cas5d ortholog, and high-resolution structural studies of a second Cas5d family member, demonstrating that Cas5d is a sequence-specific RNA endonuclease that cleaves CRISPR repeats and is thus responsible for processing of pre-crRNA. Analysis of the structural homology of Cas5d with the previously characterized Cse3 protein allows us to model the interaction of Cas5d with its RNA substrate and conclude that it is a member of a larger family of CRISPR RNA endonucleases.

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