Copyright information:Taken from "Therapeutic protein transduction of mammalian cells and mice by nucleic acid-free lentiviral nanoparticles"Nucleic Acids Research 2006;34(2):e16-e16.Published online 30 Jan 2006PMCID:PMC1356536.© The Author 2006. Published by Oxford University Press. All rights reserved () Schematic representation of expression vectors required for the protein transduction technology. Transgenes are drawn to scale. () Illustration of production and use of PTNs. (1) Transient cotransfection of (i) helper construct pWW203, (ii) pseudotyping vector pLTR-G, (iii) heterologous protein-encoding lentivector (pPOI) into the PTN production cell line HEK293-T. (2) While pWW203- and pLTR-G-encoded proteins mediated assembly of nucleic acid-free pseudotyped HIV-1-derived lentiviral nanoparticles (2a), the VPR-PC-tagged protein of interest (POI) was produced (2b) and targeted to the lentivirions (2c), where the VPR-PC tag was released by the -encoded viral protease and the native POI was encapsidated into budding PTNs (2d). (3) PTNs recovered from the culture supernatant were purified and concentrated by centrifugation and administered to target cells into which the POI was transduced (4). Abbreviations: 5′LTR, 5′ long terminal repeat; GAG, HIV-1 gene encoding core proteins; GFP, green fluorescent protein; HSVtk, virus type 1 thymidine kinase; LIS, (Cassava) linamarase; pA, polyadenylation site; P, human cytomegalovirus immediate early promoter; P, human elongation factor 1a promoter; RIPDD, RIP death domain—C-terminal domain of the human serine-threonine kinase 1 receptor; POL, gene encoding virion-associated enzymes including [*] integration-deficient integrase; VSV-G, vesicular stomatitis virus G protein; VIF/VPR/REV/TAT/VPU, HIV-1 accessory proteins; VPR, encapsidation-competent HIV-1-derived accessory protein; PC, -derived protease cleavage site.