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Architecture of a DNA-guided Cas12a

Ocampo, R. F.; Orosco, C.; Huang, B.; West, M. S.; Jain, P. K.; Taylor, D. W.

2026-03-20 biochemistry
10.64898/2026.03.19.712971 bioRxiv
Show abstract

CRISPR/Cas systems have largely been restricted to RNA-guided nucleases. Here, we present the cryo-EM structure of Acidaminococcus sp. Cas12a (AsCas12a) bound to a pseudo-DNA ({Psi}DNA) guide and RNA target, revealing how Cas12a accomplishes DNA-guided RNA recognition. The {Psi}DNA hairpin bridges the recognition and nuclease lobes, mimicking a PAM-proximal duplex and positioning the spacer to allow formation of a canonical RNA-DNA heteroduplex along the REC lobe. This provides a structural framework for its activity and provides a blueprint for future engineering.

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