title: Torsionally-strained DNA and intermolecular purine-purine-pyrimidine triple-helix formation.
abstract: A potentially powerful pharmacological approach to modulating the expression of specific, disease-related genes involves the inhibition of transcription factor binding to promoter or enhancer elements through oligonucleotide-mediated triple-helix formation. In vivo, the typical target for intermolecular triplex formation would most likely be torsionally-strained rather than relaxed duplex DNA. To determine the effects of strained DNA on triplex formation, we investigated the interactions between a G/T-rich oligonucleotide and both supercoiled and relaxed plasmid DNA using a restriction endonuclease protection assay. Both the kinetics of formation and dissociation of purine-motif triplexes were unaffected by the conformational state of the duplex DNA. Similarly, the topological state of the plasmid targets was not affected by triplex formation. Taken together, these observations suggest that stable intermolecular triplexes can form in vivo under conditions of moderate torsional strain.
authors.affiliation: Department of Tumor Biology, University of Texas M. D. Anderson Cancer Center, Houston 77030, USA.
authors.forename: M
authors.initials: M
authors.lastname: Musso
authors.forename: M W
authors.initials: MW
authors.lastname: Van Dyke
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry*; D007700:Kinetics; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*; D010957:Plasmids / Q000737:chemistry*; D011687:Purines; D011743:Pyrimidines; D015183:Restriction Mapping
chemical_list: D046911:Macromolecular Substances; D009838:Oligodeoxyribonucleotides; D011687:Purines; D011743:Pyrimidines; D004247:DNA