Direct CRISPR spacer acquisition from RNA by a natural reverse transcriptase-Cas1 fusion protein

Science. 2016 Feb 26;351(6276):aad4234. doi: 10.1126/science.aad4234.


CRISPR systems mediate adaptive immunity in diverse prokaryotes. CRISPR-associated Cas1 and Cas2 proteins have been shown to enable adaptation to new threats in type I and II CRISPR systems by the acquisition of short segments of DNA (spacers) from invasive elements. In several type III CRISPR systems, Cas1 is naturally fused to a reverse transcriptase (RT). In the marine bacterium Marinomonas mediterranea (MMB-1), we showed that a RT-Cas1 fusion protein enables the acquisition of RNA spacers in vivo in a RT-dependent manner. In vitro, the MMB-1 RT-Cas1 and Cas2 proteins catalyze the ligation of RNA segments into the CRISPR array, which is followed by reverse transcription. These observations outline a host-mediated mechanism for reverse information flow from RNA to DNA.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / classification
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Base Sequence
  • CRISPR-Associated Proteins / classification
  • CRISPR-Associated Proteins / genetics
  • CRISPR-Associated Proteins / metabolism*
  • CRISPR-Cas Systems*
  • Clustered Regularly Interspaced Short Palindromic Repeats*
  • DNA / genetics
  • Introns / genetics
  • Marinomonas / enzymology*
  • Marinomonas / genetics
  • Molecular Sequence Data
  • Mutant Chimeric Proteins / classification
  • Mutant Chimeric Proteins / genetics
  • Mutant Chimeric Proteins / metabolism*
  • Phylogeny
  • Protein Structure, Tertiary
  • RNA / genetics
  • RNA / metabolism*
  • RNA Splicing
  • RNA-Directed DNA Polymerase / classification
  • RNA-Directed DNA Polymerase / genetics
  • RNA-Directed DNA Polymerase / metabolism*


  • Bacterial Proteins
  • CRISPR-Associated Proteins
  • Mutant Chimeric Proteins
  • RNA
  • DNA
  • RNA-Directed DNA Polymerase

Associated data

  • SRA/ID-SRP066108