Structure and function of DNA transposition assemblies involved in antibiotic resistance spreading.

Transposons are mobile genetic elements that drive evolution and adaptation throughout the tree of life. In bacteria, they often transfer antibiotic resistance genes and contribute to the emergence of multidrug-resistant pathogens. In this talk, I will present our recent discoveries on a group of transposons that efficiently propagate antibiotic resistance genes across diverse microbial communities. Using a dedicated computational pipeline, we mapped the most wide-spread transposons in bacterial genomes and characterized their diversity, genetic cargo, and transfer dynamics. Selected elements were experimentally reconstituted to describe their molecular mechanisms and biochemical pathways. We determined numerous high-resolution crystal and cryo-EM structures of the protein-DNA assemblies involved in transposon movement. The structures capture various stages of transposition and reveal an intricate interplay between the core transposition machinery and host-encoded proteins. Protein interactions shape transposon and genomic DNA in unique ways to cut, exchange and re-join strands in a tightly regulated manner. Importantly, our data also explain how specific DNA distortion and cleavage mechanisms enable the transposons to move between diverse genomic sites, expanding gene transfer across many species. These results shed new light onto the molecular strategies of antibiotic resistance carrying transposons and show how they evolved to effectively spread key genetic traits. Our insights also open new opportunities to develop strategies for blocking transposition and thereby help control resistance spreading.