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-Structure paper
Title | Structural snapshots of R-loop formation by a type I-C CRISPR Cascade. |
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Journal, issue, pages | Mol Cell, Vol. 83, Issue 5, Page 746-758.e5, Year 2023 |
Publish date | Mar 2, 2023 |
Authors | Roisin E O'Brien / Jack P K Bravo / Delisa Ramos / Grace N Hibshman / Jacquelyn T Wright / David W Taylor / |
PubMed Abstract | Type I CRISPR-Cas systems employ multi-subunit Cascade effector complexes to target foreign nucleic acids for destruction. Here, we present structures of D. vulgaris type I-C Cascade at various ...Type I CRISPR-Cas systems employ multi-subunit Cascade effector complexes to target foreign nucleic acids for destruction. Here, we present structures of D. vulgaris type I-C Cascade at various stages of double-stranded (ds)DNA target capture, revealing mechanisms that underpin PAM recognition and Cascade allosteric activation. We uncover an interesting mechanism of non-target strand (NTS) DNA stabilization via stacking interactions with the "belly" subunits, securing the NTS in place. This "molecular seatbelt" mechanism facilitates efficient R-loop formation and prevents dsDNA reannealing. Additionally, we provide structural insights into how two anti-CRISPR (Acr) proteins utilize distinct strategies to achieve a shared mechanism of type I-C Cascade inhibition by blocking PAM scanning. These observations form a structural basis for directional R-loop formation and reveal how different Acr proteins have converged upon common molecular mechanisms to efficiently shut down CRISPR immunity. |
External links | Mol Cell / PubMed:36805026 / PubMed Central |
Methods | EM (single particle) |
Resolution | 2.7 - 3.1 Å |
Structure data | EMDB-27393, PDB-8dej: EMDB-27402, PDB-8dex: EMDB-27403, PDB-8dfa: EMDB-27409, PDB-8dfo: EMDB-27412, PDB-8dfs: |
Source |
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Keywords | DNA BINDING PROTEIN/DNA/RNA / type I-C Cascade / dsDNA bound / CRISPR / Cascade / type I-C / DNA BINDING PROTEIN / DNA BINDING PROTEIN-DNA-RNA complex / RNA BINDING PROTEIN/RNA / RNA BINDING PROTEIN-RNA complex / ssDNA target / anti-CRISPR / AcrIC4 / IF2 |