Unlocking the potential of CRISPR-associated transposons: from structural to functional insights.

Clustered regularly interspaced short palindromic repeats (CRISPR)-associated transposons (CASTs) are emerging genome-editing tools that enable RNA-guided DNA integration without inducing double-strand breaks (DSBs). Unlike CRISPR-associated (Cas) nucleases, CASTs use transposon machinery to insert large DNA segments with high precision, potentially reducing off-target effects and bypassing DNA damage responses. CASTs are categorized into classes 1 and 2, each employing distinct mechanisms for DNA targeting and integration. Recent structural insights have elucidated how CASTs recognize target sites, recruit transposases, and mediate insertion. These advances position CASTs as promising tools for genome engineering in bacteria and possibly in mammalian cells. Key challenges remain in enhancing efficiency and specificity, particularly for therapeutic use. Ongoing research aims to evolve CAST systems for precise, large-scale genome editing in human cells.