Figure 6.

Functional regions of a type III RNA target. Segments 2–6 drive binding of the TmaCmr complex to the RNA target, whereas the PFS (positions −1 to −5) and segment 1 (positions 1 to 5) of the RNA target regulate activation of Cas10. Noncomplementary PFSs are activating, whereas an anti-tag PFS is deactivating; this sequence is recognized by base pairing in positions −2 to −5 and a guanine base in position −1. Base pairing in segment 1 allows activation, and mismatches across this segment prevent activation.