CRISPR RNA Maturation by Trans-Encoded Small RNA and Host Factor RNase III

Nature. 2011 Mar 31;471(7340):602-7. doi: 10.1038/nature09886.

Abstract

CRISPR/Cas systems constitute a widespread class of immunity systems that protect bacteria and archaea against phages and plasmids, and commonly use repeat/spacer-derived short crRNAs to silence foreign nucleic acids in a sequence-specific manner. Although the maturation of crRNAs represents a key event in CRISPR activation, the responsible endoribonucleases (CasE, Cas6, Csy4) are missing in many CRISPR/Cas subtypes. Here, differential RNA sequencing of the human pathogen Streptococcus pyogenes uncovered tracrRNA, a trans-encoded small RNA with 24-nucleotide complementarity to the repeat regions of crRNA precursor transcripts. We show that tracrRNA directs the maturation of crRNAs by the activities of the widely conserved endogenous RNase III and the CRISPR-associated Csn1 protein; all these components are essential to protect S. pyogenes against prophage-derived DNA. Our study reveals a novel pathway of small guide RNA maturation and the first example of a host factor (RNase III) required for bacterial RNA-mediated immunity against invaders.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / immunology
  • Bacterial Proteins / metabolism
  • Conserved Sequence
  • DNA, Viral / genetics
  • DNA, Viral / metabolism
  • Escherichia coli
  • Models, Biological
  • Prophages / genetics
  • RNA Precursors / genetics
  • RNA Precursors / metabolism
  • RNA Processing, Post-Transcriptional
  • RNA, Bacterial / biosynthesis
  • RNA, Bacterial / genetics*
  • RNA, Bacterial / immunology
  • RNA, Bacterial / metabolism*
  • RNA, Guide / genetics*
  • Ribonuclease III / metabolism*
  • Streptococcus pyogenes / genetics*
  • Streptococcus pyogenes / immunology*
  • Streptococcus pyogenes / metabolism
  • Streptococcus pyogenes / virology

Substances

  • Bacterial Proteins
  • DNA, Viral
  • RNA Precursors
  • RNA, Bacterial
  • RNA, Guide
  • Ribonuclease III