Intein-mediated cytoplasmic reconstitution of a split toxin enables selective cell ablation in mixed populations and tumor xenografts

Significance Protein reconstitution via transsplicing by split inteins is an indispensable tool in protein engineering, biotechnology, and experimental therapeutics. In living cells, the application of split inteins has been limited to their nonspecific delivery or expression from genetic elements, which come with substantial limitations in specificity of targeting and temporal control of expression and generation of the transspliced product. To overcome these limitations we designed a protocol for delivering the split-intein protein fragments to the cell cytoplasm via a receptor-specific toxin-based delivery machinery. We achieved a precisely controlled reconstitution of a functional catalytic domain of diphtheria toxin from its two dysfunctional fragments, one expressed and one delivered as a protein, in selective subpopulations of cells in mixed cultures and in vivo.