Abstract

CRISPR–Cas effectors typically rely on RNA guides to recognize target sequences. In Cas12a, the protospacer adjacent motif on DNA engages conserved protein residues, triggering target binding and nuclease activation. Here we reprogram Cas12a into a DNA-guided, RNA-targeting effector. Exploiting protospacer-adjacent motif-dependent interaction, we engineer synthetic CRISPR DNA that engages Cas12a to form a functional deoxyribonucleoprotein complex, while repurposing solely RNA as the programmable target. Structural, biophysical and biochemical analyses reveal the molecular basis of this DNA-guided, RNA-targeting configuration and support an activation pathway distinct from that of canonical RNA-guided systems. DNA-guided Cas12a enables direct RNA detection and efficient intracellular RNA knockdown, establishing a modular activation architecture for CRISPR–Cas12a and expanding the design space for programmable RNA manipulation.