Synthetic Type III-E CRISPR-Cas Effectors for Programmable RNA-targeting.

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• CRISPR-Cas systems are crucial for adaptive immunity in prokaryotes.
• The type III-E CRISPR-Cas effector class, a recently discovered group, consists of fused Cas7 and Cas11 domains for RNA targeting.
• Understanding the modularity and evolutionary flexibility of these systems is key to harnessing their potential.

Purpose of the Study:

• To identify and characterize novel type III-E-like CRISPR-Cas effectors.
• To investigate the domain modularity and engineering potential of type III-E effectors.
• To develop a new method for creating chimeric RNA-targeting Cas effectors.

Main Methods:

• Bioinformatic identification of novel CRISPR-Cas effector sequences.
• Protein domain analysis and comparison of type III-E effector components.
• Functional characterization of engineered chimeric CRISPR-Cas effectors through domain swapping and additions.

Main Results:

• A novel type III-E-like effector, comprising three Cas7 domains and a Cas1 domain, was identified.
• This novel effector was inactive but successfully engineered into an active RNA-targeting Cas effector.
• Domain swapping experiments demonstrated significant flexibility within type III-E effector architecture, including successful exchange of Cas1 and Cas11 domains.

Conclusions:

• Type III-E CRISPR-Cas effector domains exhibit remarkable modularity, allowing for functional interchangeability between different effectors.
• Natural blueprints of type III-E effectors provide a framework for engineering novel, active RNA-targeting Cas systems.
• This work establishes a new paradigm for designing and engineering CRISPR-Cas tools by leveraging domain plasticity.