title: Inhibition of gene transcription by purine rich triplex forming oligodeoxyribonucleotides.
abstract: Several oligodeoxynucleotides (ODNs) were designed in order to interact with the purine rich element of the IRE (Interferon Responsive Element) of the 6-16 gene by triplex formation. An ODN of 21 bases, the sequence being identical to that of the purine strand of the IRE (48% G), but in reverse orientation, was able to interact with the IRE (KD: 20 nM). The binding was Mg2+ dependent. The two purine strands of the triplex were oriented antiparallel as confirmed by DNAase I and copper-phenanthroline footprinting experiments. An ODN in which A were replaced by T, also interacted with the same target, but with a lower affinity. Exonuclease III action indicated that the two IRE repeats of the 6-16 promoter interacted with each other through Hoogsteen base pairing, the third strand being parallel to the paired Watson-Crick strand. This led to a potential H-DNA structure which could be destabilized by adding ODNs able to form a triplex structure. 6-16 IRE driven-reporter gene constructs lost their interferon stimulability when co-transfected with triplex forming ODNs. The range of effective ODN concentrations was compatible with the affinity determined when measuring their direct interactions with the DNA.
authors.affiliation: Institut de Génétique Moléculaire, UMR 9942, CNRS, Montpellier, France.
authors.forename: C
authors.initials: C
authors.lastname: Roy
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003850:Deoxyribonuclease I; D007372:Interferons / Q000494:pharmacology*; D008274:Magnesium / Q000494:pharmacology; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D010618:Phenanthrolines; D010957:Plasmids; D011687:Purines / Q000737:chemistry; D013329:Structure-Activity Relationship; D014158:Transcription, Genetic / Q000187:drug effects*; D014162:Transfection
chemical_list: D009838:Oligodeoxyribonucleotides; D010618:Phenanthrolines; D011687:Purines; D004247:DNA; D007372:Interferons; D003850:Deoxyribonuclease I; D008274:Magnesium; C025205:1,10-phenanthroline