Prime assembly enables targeted DNA integration in human cells

Researchers have developed "prime assembly," a new genome editing technique that enables targeted integration of medium-to-large DNA sequences in human cells without requiring double-strand breaks or cell cycle progression. The method works in both dividing and non-dividing cells. Prime assembly leverages CRISPR-targeted dual flap synthesis to install single or double-stranded DNA fragments at specific genomic sites. The approach successfully performed exon recoding, transgene integration, and megabase-scale rearrangements in primary human cells, including therapeutically relevant loci. The technique expands genome engineering capabilities by avoiding reliance on double-stranded DNA donors, nuclease-driven breaks, or cell division. This offers potential advantages over homology-directed repair for therapeutic applications in difficult-to-edit cell types.