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Updated: Jan 21, 2026
11:53
Substrate Generation for Endonucleases of CRISPR/Cas Systems
Published on: September 8, 2012
28.0K
CRISPR DNA elements controlling site-specific spacer integration and proper repeat length by a Type II CRISPR-Cas
Jenny G Kim1, Sandra Garrett2, Yunzhou Wei1
1Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA.
Nucleic Acids Research
|August 9, 2019
Summary
CRISPR-Cas systems use Cas1 and Cas2 proteins to precisely integrate viral DNA spacers into bacterial CRISPR loci. This process ensures accurate repeat duplication for effective antiviral immunity in Streptococcus thermophilus.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- CRISPR-Cas systems confer adaptive immunity in prokaryotes against viruses.
- Spacer acquisition integrates foreign DNA into CRISPR loci for heritable immunity.
Purpose of the Study:
- Investigate DNA elements controlling accurate spacer uptake in Streptococcus thermophilus type II-A CRISPR loci.
- Elucidate the mechanism of spacer integration catalyzed by Cas1 and Cas2 proteins.
Main Methods:
- Purified Cas1 and Cas2 proteins were used to study spacer integration.
- Analysis of leader sequence elements and repeat junctions involved in integration specificity.
Main Results:
- Cas1 and Cas2 proteins exhibit high specificity for CRISPR repeat junctions.
- A 10 bp leader sequence is critical for polarized spacer integration near the leader.
- Spacer integration involves a two-step transesterification reaction targeting repeat borders.
- Integration site selection is directed by leader-repeat junction recognition and length-defining mechanisms.
Conclusions:
- Type II Cas1/Cas2 proteins coordinate directional and site-specific spacer integration.
- Precise repeat duplication is ensured, which is essential for CRISPR immunity.
- Understanding this mechanism is key to harnessing CRISPR-Cas for biotechnology.
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