Casμ, a novel class of miniature type-V Cas12f nucleases with diverse PAM

Abstract

Small CRISPR-Cas effectors are key to developing gene editing therapies due to the packaging constraints in viral vectors. While Cas9 and Cas12a CRISPR-Cas effectors have advanced into select clinical applications, their size is prohibitive for efficient delivery of both nuclease and guide RNA in a single viral vector. Type-V Cas12f effectors present a solution given their small size. Here we describe Cas, a novel class of miniature (<490AA) type-V Cas12f nucleases that cleave double stranded DNA in human cells. We determined their optimal trans-activating RNA (tracrRNA) empirically through rational modifications which resulted in an optimal single guide RNA (sgRNA). We show that the Cas nucleases have broader PAM preferences than previously known Cas12f effectors. The unique characteristics of these novel nucleases add to the diversity of the miniature CRISPR-Cas toolbox while the expanded PAM allows for the editing of genomic locations that could not be accessed with existing Cas12f nucleases.