EFFICIENT TRANSFORMATION OF MAMMALIAN-CELLS USING DNA INTERPOLYELECTROLYTE COMPLEXES WITH CARBON-CHAIN POLYCATIONS

A new method for mammalian cell transformation is proposed which is ba sed on incorporation of plasmids into interpolyelectrolyte complexes ( IPECs) with carbon chain polycations. The method is illustrated by exa mples of pRSV CAT and pbeta-Gal plasmid IPECs with poly(N-ethyl-4-viny lpyridinium bromide) (C2PVP) and 4-vinylpyridinium)-poly(N-cetyl-4-vin ylpyridinium) bromides random copolymer (C-16PVP). These IPECs are pro duced spontaneously due to formation of a cooperative system of interc hain electrostatic bonds after mixing DNA and polycation solutions. Th e interaction of IPEC with normal mouse fibroblasts NIH 3T3, human T-l ymphoma ''Jurkat'', and Mardin Darby canine kidney cells has been stud ied. The data obtained has revealed that plasmid incorporation into IP ECs significantly enhances both DNA adsorption on the plasma membrane and DNA uptake into a cell. The in vitro transformation of NIH 3T3 cel ls was monitored by a standard cloramphenicol acetyltransferase (CAT) assay (pRSV CAT plasmid) and by detection of beta-galactosidase (beta- Gal) expression using 4-methylumbeliferril beta-D-galactopyranoside as a substrate (pbeta-Gal plasmid). In both cases it has been proved tha t IPEC-incorporated plasmids possess an ability for efficient cell tra nsformation. The transforming activity of IPECs depends on their compo sition and polycation chemical structure. Under optimal conditions the efficiency of cell transformation with IPECs is several fold higher t han that observed during standard calcium phosphate precipitation. The mechanism of the phenomenon observed is discussed. According to this mechanism polycations form positively charged loops fixed on DNA molec ules. These loops interact with negatively charged lipids on plasma me mbranes, which probably induces effective endocytosis and subsequent c ell transformation.