Structural insights into the regulation of Cas7-11 by TPR-CHAT

The CRISPR-guided caspase (Craspase) complex is an assembly of the target-specific RNA nuclease known as Cas7-11 bound to CRISPR RNA (crRNA) and an ancillary protein known as TPR-CHAT (tetratricopeptide repeats (TPR) fused with a CHAT domain). The Craspase complex holds promise as a tool for gene therapy and biomedical research, but its regulation is poorly understood. TPR-CHAT regulates Cas7-11 nuclease activity via an unknown mechanism. In the present study, we use cryoelectron microscopy to determine structures of the Desulfonema magnum (Dm) Craspase complex to gain mechanistic insights into its regulation. We show that DmTPR-CHAT stabilizes crRNA-bound DmCas7-11 in a closed conformation via a network of interactions mediated by the DmTPR-CHAT N-terminal domain, the DmCas7-11 insertion finger and Cas11-like domain, resulting in reduced target RNA accessibility and cleavage.

Automated summary

The CRISPR-guided caspase (Craspase) complex consists of Cas7-11, CRISPR RNA (crRNA), and TPR-CHAT protein. It shows potential as a tool for gene therapy and biomedical research, but its regulation is not well understood. In this study, cryoelectron microscopy was used to determine the structures of the Dm Craspase complex to understand its regulation mechanism. It was found that DmTPR-CHAT stabilizes crRNA-bound DmCas7-11 in a closed conformation through interactions mediated by DmTPR-CHAT N-terminal domain, DmCas7-11 insertion finger, and Cas11-like domain, resulting in reduced target RNA accessibility and cleavage.