EMD-29040
Cryo-EM structure of Cascade-DNA-fullRloop in type I-B CAST system
EMD-29040
Single-particle3.13 Å
Deposition: 07/12/2022Map released: 09/08/2023
Last modified: 31/01/2024
Sample Organism:
Nostoc sp. 'Peltigera membranacea cyanobiont' 210A,
synthetic construct,
Peltigera membranacea
Sample: Ternary complex of Cascade proteins, crRNA and target DNA with the complete R loop formed.
Fitted models: 8ff5 (Avg. Q-score: 0.372)
Deposition Authors: Chang L
,
Wang S
Sample: Ternary complex of Cascade proteins, crRNA and target DNA with the complete R loop formed.
Fitted models: 8ff5 (Avg. Q-score: 0.372)
Deposition Authors: Chang L
,
Wang S
Molecular mechanism for Tn7-like transposon recruitment by a type I-B CRISPR effector.
Abstract:
Tn7-like transposons have co-opted CRISPR-Cas systems to facilitate the movement of their own DNA. These CRISPR-associated transposons (CASTs) are promising tools for programmable gene knockin. A key feature of CASTs is their ability to recruit Tn7-like transposons to nuclease-deficient CRISPR effectors. However, how Tn7-like transposons are recruited by diverse CRISPR effectors remains poorly understood. Here, we present the cryo-EM structure of a recruitment complex comprising the Cascade complex, TniQ, TnsC, and the target DNA in the type I-B CAST from Peltigera membranacea cyanobiont 210A. Target DNA recognition by Cascade induces conformational changes in Cas6 and primes TniQ recruitment through its C-terminal domain. The N-terminal domain of TniQ is bound to the seam region of the TnsC spiral heptamer. Our findings provide insights into the diverse mechanisms for the recruitment of Tn7-like transposons to CRISPR effectors and will aid in the development of CASTs as gene knockin tools.
Tn7-like transposons have co-opted CRISPR-Cas systems to facilitate the movement of their own DNA. These CRISPR-associated transposons (CASTs) are promising tools for programmable gene knockin. A key feature of CASTs is their ability to recruit Tn7-like transposons to nuclease-deficient CRISPR effectors. However, how Tn7-like transposons are recruited by diverse CRISPR effectors remains poorly understood. Here, we present the cryo-EM structure of a recruitment complex comprising the Cascade complex, TniQ, TnsC, and the target DNA in the type I-B CAST from Peltigera membranacea cyanobiont 210A. Target DNA recognition by Cascade induces conformational changes in Cas6 and primes TniQ recruitment through its C-terminal domain. The N-terminal domain of TniQ is bound to the seam region of the TnsC spiral heptamer. Our findings provide insights into the diverse mechanisms for the recruitment of Tn7-like transposons to CRISPR effectors and will aid in the development of CASTs as gene knockin tools.