Broad use of CRISPR-Cas12a (formerly Cpf1) nucleases 1 has been hindered by the requirement for an extended TTTV protospacer adjacent motif (PAM) 2 . To address this limitation, we engineered an enhanced Acidaminococcus sp. Cas12a variant (enAsCas12a) that has a substantially expanded targeting range, enabling targeting of many previously inaccessible PAMs. On average, enAsCas12a exhibits two-fold higher genome editing activity on sites with canonical TTTV PAMs compared to wild-type AsCas12a, and we successfully grafted a subset of mutations from enAsCas12a onto other previously described AsCas12a variants 3 to enhance their activities. enAsCas12a improves the efficiency of multiplex gene editing, endogenous gene activation, and C-to-T base editing, and we engineered a high-fidelity version of enAsCas12a (enAsCas12a-HF1) to reduce off-target effects. Both enAsCas12a and enAsCas12a-HF1 function in HEK293T and primary human T cells when delivered as ribonucleoprotein (RNP) complexes. Collectively, enAsCas12a provides an optimized version of Cas12a that should enable wider application of Cas12a enzymes for gene and epigenetic editing. [AU: Revised abstract OK?]

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Targeted and inducible regulation of mammalian gene expression is a broadly important capability. We engineered drug-inducible catalytically inactive Cpf1 fused to transcriptional activation domains to tune the expression of endogenous genes in human cells. Leveraging the multiplex capability of the Cpf1 platform, we demonstrate both synergistic and combinatorial gene expression in human cells. Our work should enable the development of multiplex gene perturbation library screens for understanding complex cellular phenotypes.

Prime Editors have been delivered using DNA or mRNA vectors. Here we demonstrate prime editing (PE) with purified ribonucleoprotein (RNP) complexes. We introduced somatic mutations in zebrafish embryos with frequencies as high as 30% and demonstrate germline transmission. We also observed unintended insertions, deletions and pegRNA scaffold incorporations. In HEK293T and primary human T cells, PE RNP complexes introduced desired edits with frequencies of up to 21% and 7.5%, respectively.