Casposase structure and the mechanistic link between DNA transposition and spacer acquisition by CRISPR-Cas
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, United States
Abstract
Key to CRISPR-Cas adaptive immunity is maintaining an ongoing record of invading nucleic acids, a process carried out by the Cas1-Cas2 complex that integrates short segments of foreign genetic material (spacers) into the CRISPR locus. It is hypothesized that Cas1 evolved from casposases, a novel class of transposases. We show here that the Methanosarcina mazei casposase can integrate varied forms of the casposon end in vitro, and recapitulates several properties of CRISPR-Cas integrases including site-specificity. The X-ray structure of the casposase bound to DNA representing the product of integration reveals a tetramer with target DNA bound snugly between two dimers in which single-stranded casposon end binding resembles that of spacer 3'-overhangs. The differences between transposase and CRISPR-Cas integrase are largely architectural, and it appears that evolutionary change involved changes in protein-protein interactions to favor Cas2 binding over tetramerization; this in turn led to preferred integration of single spacers over two transposon ends.
Data availability
Diffraction data for the casposase-DNA complex have been deposited under PBD ID 6OPM. The GSE number for the NGS data is GSE139037.
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Casposase structure and the mechanistic link between DNA transposition and spacer acquisition by CRISPR-CasNCBI Gene Expression Omnibus, GSE139037.
Article and author information
Author details
Funding
National Institute of Diabetes and Digestive and Kidney Diseases (Intramural Program)
- Alison B Hickman
- Shweta Kailasan
- Pavol Genzor
- Astrid D Haase
- Fred Dyda
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.
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Casposase structure and the mechanistic link between DNA transposition and spacer acquisition by CRISPR-Cas
eLife 9:e50004.
https://doi.org/10.7554/eLife.50004
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