Structural snapshots of R-loop formation by a type I-C CRISPR Cascade

O’Brien RE, Bravo JPK, Ramos D, Hibshman GN, Wright JT, Taylor DW. 2023. Structural snapshots of R-loop formation by a type I-C CRISPR Cascade. Molecular Cell. 83(5), 746–758.e5.

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Journal Article | Published | English

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Author
O’Brien, Roisin E.; Bravo, JackISTA ; Ramos, Delisa; Hibshman, Grace N.; Wright, Jacquelyn T.; Taylor, David W.
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 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.
Publishing Year
Date Published
2023-03-02
Journal Title
Molecular Cell
Volume
83
Issue
5
Page
746-758.e5
ISSN
IST-REx-ID

Cite this

O’Brien RE, Bravo JPK, Ramos D, Hibshman GN, Wright JT, Taylor DW. Structural snapshots of R-loop formation by a type I-C CRISPR Cascade. Molecular Cell. 2023;83(5):746-758.e5. doi:10.1016/j.molcel.2023.01.024
O’Brien, R. E., Bravo, J. P. K., Ramos, D., Hibshman, G. N., Wright, J. T., & Taylor, D. W. (2023). Structural snapshots of R-loop formation by a type I-C CRISPR Cascade. Molecular Cell. Elsevier. https://doi.org/10.1016/j.molcel.2023.01.024
O’Brien, Roisin E., Jack Peter Kelly Bravo, Delisa Ramos, Grace N. Hibshman, Jacquelyn T. Wright, and David W. Taylor. “Structural Snapshots of R-Loop Formation by a Type I-C CRISPR Cascade.” Molecular Cell. Elsevier, 2023. https://doi.org/10.1016/j.molcel.2023.01.024.
R. E. O’Brien, J. P. K. Bravo, D. Ramos, G. N. Hibshman, J. T. Wright, and D. W. Taylor, “Structural snapshots of R-loop formation by a type I-C CRISPR Cascade,” Molecular Cell, vol. 83, no. 5. Elsevier, p. 746–758.e5, 2023.
O’Brien RE, Bravo JPK, Ramos D, Hibshman GN, Wright JT, Taylor DW. 2023. Structural snapshots of R-loop formation by a type I-C CRISPR Cascade. Molecular Cell. 83(5), 746–758.e5.
O’Brien, Roisin E., et al. “Structural Snapshots of R-Loop Formation by a Type I-C CRISPR Cascade.” Molecular Cell, vol. 83, no. 5, Elsevier, 2023, p. 746–758.e5, doi:10.1016/j.molcel.2023.01.024.
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