Repeat Size Determination by Two Molecular Rulers in the Type I-E CRISPR Array

Moran G. Goren, Shany Doron, Rea Globus, Gil Amitai, Rotem Sorek*, Udi Qimron

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Prokaryotic adaptive immune systems are composed of clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas) proteins. These systems adapt to new threats by integrating short nucleic acids, termed spacers, into the CRISPR array. The functional motifs in the repeat and the mechanism by which a constant repeat size is maintained are still elusive. Here, through a series of mutations within the repeat of the CRISPR-Cas type I-E, we identify motifs that are crucial for adaptation and show that they serve as anchor sites for two molecular rulers determining the size of the new repeat. Adaptation products from various repeat mutants support a model in which two motifs in the repeat bind to two different sites in the adaptation complex that are 8 and 16 bp away from the active site. This model significantly extends our understanding of the adaptation process and broadens the scope of its applications.

Original languageEnglish
Pages (from-to)2811-2818
Number of pages8
JournalCell Reports
Issue number11
StatePublished - 13 Sep 2016


  • adaptation
  • anchor site
  • elongated repeat
  • shortened repeat
  • spacer integration


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