Structural insight into IscB's RNA-lid-based inactivation mechanism - PubMed
4 hours ago
- #genome editing
- #IscB
- #structural biology
- IscB is a compact Cas9 ancestor with potential as a programmable genome editor due to its small size.
- The study presents cryo-EM structures showing IscB's transition from a resting state to activation via guide-target pairing.
- A dual inactivation mechanism involves RNA lids blocking the HNH domain and occluding the RuvC active site.
- Guide RNA displacement resembles a 'car pedal' motion, triggering activation at 11-nt pairing.
- The HNH domain uses an R-wedge motif for R-loop stabilization and undergoes a ~90° rotation via hinge regions.
- Engineering hinge motifs in IscBHig1 and IscBHig2 variants improved genome-editing efficiency in cells.
- The research reveals IscB's autoinhibition and activation mechanisms, identifying hinge elements as targets for engineering efficient editors.