The pCMV-PE2 (Addgene plasmid #132775) and pU6-pegRNA-GG-acceptor (Addgene plasmid #132777) plasmids were a gift from David Liu. pegRNA-encoding plasmids were generated by Golden Gate assembly using a custom acceptor plasmid according to methods described in a previous paper. (23 (link)) pCMV-PE2 was modified to generate a set of plasmids encoding the PE2 variants, which included pCMV-PE2-HF (N497A, R661A, Q695A and Q926A), pCMV-ePE2 (K848A, K1003A and R1060A), pCMV-Evo-PE2 (M495V, Y515N, K526E and R661Q), pCMV-Hypa-PE2 (N692A, M694A, Q695A and H698A) and pCMV-Sniper-PE2 (F539S, M763I and K890N), by incorporating mutations via NEBuilder® HiFi DNA Assembly Master Mix (New England Biolabs) with gblocks containing mutations (IDT) and site-directed mutagenesis (Q5 Site-Directed Mutagenesis Kit, New England Biolabs).