Experimental strategy for characterization of novel TnpB orthologs.

TnpB proteins encoded in IS200/IS605 and IS607 mobile genetic elements are among the most widespread proteins in the microbial world. They function as RNA-guided DNA nucleases that play a critical role in transposon proliferation and are the predecessors of CRISPR-Cas12 effector proteins of the type V CRISPR-Cas family. Small size of TnpB nucleases makes them an attractive alternative for larger Cas9 and Cas12 proteins in genome editing applications. However, only a small fraction of TnpB nucleases characterized to date are active in human cells, highlighting the need to identify new TnpB variants that can function as genome editors. Here, we present an experimental pipeline for the characterization of TnpB proteins by combining in silico analysis with in vitro assays. To validate it we determined guide RNA and identified TAM for a set of TnpB orthologs. The proposed workflow can be employed for rapid screening and characterization of the huge TnpB protein family to identify novel TnpB variants that might expand the genome editing toolbox.