SCOPE enables type III CRISPR-Cas diagnostics using flexible targeting and stringent CARF ribonuclease activation

Area of Science:

• Molecular Biology
• Immunology
• Biotechnology

Background:

• Type III CRISPR-Cas systems mediate adaptive immunity through RNA recognition and cleavage.
• These systems produce cyclic oligoadenylate (cOA) second messengers.

Purpose of the Study:

• To elucidate the distinct roles of crRNA regions in type III CRISPR-Cas system functions.
• To investigate how variations in CRISPR-Cas complex composition affect crRNA recognition.
• To develop a novel diagnostic tool based on these findings.

Main Methods:

• Analysis of crRNA structure-function relationships in target RNA binding, cleavage, and cOA production.
• Characterization of type III CRISPR-Cas complex heterogeneity.
• Development and validation of the SCOPE diagnostic assay.

Main Results:

• An exposed 3' seed region of crRNA is critical for target RNA binding and cleavage.
• 5' end base pairing of crRNA is essential for cOA production.
• Variable CRISPR-Cas complex composition leads to diverse seed regions, potentially enhancing host defense.
• The SCOPE tool achieved atto-molar sensitivity for SARS-CoV-2 detection.

Conclusions:

• CRISPR-Cas systems exhibit sophisticated regulatory mechanisms involving distinct crRNA elements.
• CRISPR-Cas complex diversity contributes to robust immunity and host protection.
• The developed SCOPE diagnostic tool demonstrates high sensitivity for viral detection.