The compact Casπ (Cas12l) 'bracelet' provides a unique structural platform for DNA manipulation

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• CRISPR-Cas systems are prokaryotic immune systems and versatile gene editing tools.
• Existing CRISPR-Cas nucleases like Cas9 and Cas12 have distinct architectures and functionalities.

Purpose of the Study:

• To discover and characterize a novel, miniature CRISPR-Cas system for nucleic acid manipulation.
• To elucidate the structure and function of this new system for potential applications in gene editing.

Main Methods:

• Environmental metagenomic screening to identify new CRISPR-Cas modules.
• Biochemical assays to determine DNA cleavage activity and PAM specificity.
• Cryo-electron microscopy (Cryo-EM) to resolve the effector's molecular architecture.
• Mammalian cell experiments to assess gene editing efficiency.

Main Results:

• Discovery of a miniature type V CRISPR-Casπ (Cas12l) system (~860 aa) from environmental DNA.
• Casπ (Cas12l) utilizes a large guide RNA and recognizes a unique 5' C-rich PAM for DNA cleavage.
• Cryo-EM revealed a distinct 'bracelet' architecture, differing from canonical Cas nucleases.
• Demonstrated gene editing capability in mammalian cells with this compact system.

Conclusions:

• CRISPR-Casπ (Cas12l) represents a novel and compact DNA editing platform.
• Its unique architecture expands the understanding of CRISPR-DNA targeting mechanisms.
• This system offers a promising tool for diverse gene manipulation applications.