TRIPLE-HELICES TARGETED TO THE POLYPURINE TRACT OF A MURINE RETROVIRUS

The all-purine 13-mer oligodeoxyribonucleotide d(GGGGGGAAAAAGA), conta ining an unusually large block of contiguous guanines, was shown by el ectrophoresis and thermoelution to form a specific, 'antiparallel' com plex with the duplex containing the polypurine tract of murine retrovi ruses. Fourier transform infra-red spectroscopy (FTIR) and molecular m odeling indicated that the complex is based on reverse Hoogsteen G(GC) and A(AT) triplets, with anti orientations of the bases and with all the strands having S-type sugar conformations. This G + A-containing 1 3-mer and a G + T-containing 22-mer, d(TGTTTGTTTGGGGGGTTTTTGT), aimed at the same target, retarded in a sequence-specific manner the spreadi ng of the Friend retrovirus in Dunni cells infected de novo, thus indi cating that the polypurine tract of retroviruses may be a suitable tar get for anti-gene action.