Modularity and diversity of target selectors in Tn7 transposons

To spread, transposons must integrate into target sites without disruption of essential genes while avoiding host defense systems. Tn7-like transposons employ multiple mechanisms for target site selection, including protein-guided targeting via TnsD or TnsE and, in CRISPR-associated transposons (CASTs), RNA-guided targeting. Combining phylogenomic and structural analyses, we conducted a broad survey of target selectors, revealing diverse mechanisms used by Tn7 to recognize target sites, and experimentally characterized those TEs. Our findings reveal that Tn7 transposons employ modular architecture and co-opt target selectors from various systems to optimize target selection and drive transposon spread.