Researchers at UC Berkeley’s Innovative Genomics Institute reported a protein‑engineering strategy that inserts multiple nuclear localization signals into internal loops of Cas9 to increase nuclear import and editing efficiency in human T cells. The modification sidesteps expression problems seen with long terminal NLS tails and preserves protein stability for production. The team showed improved gene editing outcomes in primary human cells, a potential step toward more efficient ex vivo cell therapies. The approach focuses on rational structural engineering to improve intracellular delivery of gene editors without changing delivery vectors.