title: Triple helix formation with short oligonucleotide-intercalator conjugates matching the HIV-1 U3 LTR end sequence.
abstract: In an attempt to target short purine sequences in view of pharmacological application, we have synthesized three new TFO (triple-helix-forming oligonucleotide) conjugates in which an intercalating oxazolopyridocarbazole (OPC) chromophore is linked by a pentamethylene linker to a 7-mer oligonucleotide matching the polypurine/polypyrimidine sequence located in the HIV-1 U3 LTR end region. The TFO moiety of conjugates are 5'CCTTCCC, 5'GGGAAGG, and 5'GGGTTGG. Their ability to bind to double-stranded DNA targets was examined. This binding is demonstrated by a footprinting technique using DNase I as a cleaving agent. The complex involved intermolecular pyr-pur*pyr or pur-pur*pyr triple helix. Pyrimidine TFO-OPC binds in a pH-dependent manner, whereas the others do not. The formation of the complex has been investigated at neutral pH and increasing temperature. We observed that the protection due to the purine and mixed TFO-OPC was pH independent and remained identical up to 40 degrees C. To determine the position of the OPC chromophore, molecular modeling was undertaken on the purine-conjugate/target complex. It has been suggested that the complex involved the intercalation of the OPC at the triplex-duplex junction with a small unwinding at the next excluded site.
authors.affiliation: Laboratoire de Physicochimie et de Pharmacologie des Macromolécules Biologiques, Institut Gustave-Roussy, CNRS URA 147, INSERM, Villejuif, France.
authors.forename: J F
authors.initials: JF
authors.lastname: Mouscadet
authors.forename: C
authors.initials: C
authors.lastname: Ketterlé
authors.forename: H
authors.initials: H
authors.lastname: Goulaouic
authors.forename: S
authors.initials: S
authors.lastname: Carteau
authors.forename: F
authors.initials: F
authors.lastname: Subra
authors.forename: M
authors.initials: M
authors.lastname: Le Bret
authors.forename: C
authors.initials: C
authors.lastname: Auclair
mesh_terms: D001483:Base Sequence; D002227:Carbazoles / Q000737:chemistry; D004279:DNA, Viral / Q000737:chemistry* / Q000187:drug effects; D016325:HIV Long Terminal Repeat; D015497:HIV-1 / Q000235:genetics*; D006863:Hydrogen-Ion Concentration; D007364:Intercalating Agents / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*; D013696:Temperature
chemical_list: D002227:Carbazoles; D004279:DNA, Viral; D007364:Intercalating Agents; D009838:Oligodeoxyribonucleotides; C061416:oxazolopyridocarbazole