Affiliation:
1. Montana State University
2. Simons Electron Microscopy Center
3. New York Structural Biology Center
4. Scripps Research
Abstract
Abstract
Bacteria and archaea acquire resistance to viruses and plasmids by integrating fragments of foreign DNA into the first repeat of a CRISPR array. However, the mechanism of site-specific integration remains poorly understood. Here, we determine a 560 kDa integration complex structure that explains how Cas (Cas1-2/3) and non-Cas proteins (IHF) fold 150 base-pairs of host DNA into a U-shaped bend and a loop that protrude from Cas1-2/3 at right angles. The U-shaped bend traps foreign DNA on one face of the Cas1-2/3 integrase, while the loop places the first CRISPR repeat in the Cas1 active site. Both Cas3s rotate 100-degrees to expose DNA binding sites on either side of the Cas2 homodimer, that each bind an inverted repeat motif in the leader. Leader sequence motifs direct Cas1-2/3-mediated integration to diverse repeat sequences that have a 5’-GT.
Publisher
Research Square Platform LLC
Reference102 articles.
1. Evolution of adaptive immunity from transposable elements combined with innate immune systems;Koonin EV;Nat. Rev. Genet.,2015
2. McCLINTOCK, B. The origin and behavior of mutable loci in maize. Proc. Natl. Acad. Sci. U. S. A. 36, 344–355 (1950).
3. CRISPR Immunological Memory Requires a Host Factor for Specificity;Nuñez JK;Mol. Cell,2016
4. Fagerlund, R. D. et al. Spacer capture and integration by a type I-F Cas1–Cas2-3 CRISPR adaptation complex. Proc. Natl. Acad. Sci. 114, 201618421 (2017).
5. Structures of the CRISPR genome integration complex;Wright AV;Science,2017