Enhancing Prime Editing Efficiency and Flexibility with Tethered and Split pegRNAs

Prime editing (PE) has advantages for small insertion, deletion or point mutations without double-stranded DNA breaks. The 3’-extension of pegRNAs could negatively affect its stability or folding and comprise the PE activity. Here we generated s tem-loop PEs (sPEs) by adding stem-loop aptamers at the 3’-terminal of pegRNA, which can be tethered to Cas9 nickase resulting in tethered PEs (tPEs). sPEs and tPEs increased the small insertion, deletion or point mutations efficiency by 2-4-fold on average in HEK293, U2OS and HeLa cells. We split the modified pegRNAs into sgRNA and prime RNA. The resulting s plit pegR N A prime editors (SnPEs) maintain the PE activity and increase flexibility.