Structural insights into RNA-guided RNA editing by the Cas13b-ADAR2 complex

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• CRISPR-Cas13 systems are RNA-guided RNA endonucleases utilized in RNA targeting technologies.
• RNA editing for programmable A-to-I replacement (REPAIR) technology uses catalytically inactive Cas13b fused to ADAR2 for transcript editing.
• This technology holds promise for gene therapy applications.

Purpose of the Study:

• To determine the cryo-electron microscopy structures of various Cas13-RNA complexes.
• To gain mechanistic insights into RNA cleavage and editing processes mediated by Cas13.
• To engineer a more compact and efficient Cas13-ADAR2 complex for enhanced RNA editing.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was employed to resolve complex structures.
• Structural analysis of PspCas13b-guide RNA binary complex.
• Structural analysis of ternary complexes involving PspCas13b, guide RNA, and target RNA, including the dPspCas13b-ADAR2 fusion.

Main Results:

• Detailed structures of key Cas13-RNA complexes were obtained.
• Mechanistic insights into RNA cleavage and adenosine-to-inosine editing were provided.
• A compact and efficient REPAIR-mini complex was engineered based on structural findings.

Conclusions:

• The study advances the understanding of CRISPR-Cas13 effector nucleases.
• Structural insights facilitate the mechanism of RNA editing by dPspCas13b-ADAR2.
• Findings pave the way for developing improved RNA-targeting technologies and gene therapies.