POLY(L-LYSINE)-GRAFT-DEXTRAN COPOLYMER - AMAZING EFFECTS ON TRIPLEX STABILIZATION UNDER PHYSIOLOGICAL PH AND IONIC CONDITIONS (IN-VITRO)

Tripler DNA formation involving unmodified triplex-forming oligonucleo tides (TFOs) is very unstable under physiological conditions. Here, we report a novel strategy to stabilize both purine and pyrimidine motif tripler DNA within the rat al (I) collagen gene promoter Under physio logically relevant conditions by a poly(L-lysine)-graft-dextran copoly mer. Using an in vitro electrophoretic mobility shift assay, we show t hat the copolymer almost completely abrogates the inhibitory effects o f physiological concentrations of monovalent cations, particularly pot assium ion (K+), on purine motif tripler formation involving very tow concentrations of an unmodified guanine-rich TFO, Of importance, pH de pendency in pyrimidine motif tripler formation involving an unmodified cytosine-rich TFO is also significantly overcome by the copolymer, Fi nally, the triplex-stabilizing efficiency of the copolymer is remarkab ly higher than that of other oligocations, like spermine and spermidin e. We suggest that the ability of the graft copolymer to stabilize tri pler DNA under physiologically relevant pH and salt concentrations wil l be a cue for further progress in the antigene strategy.