title: Alternate strand recognition of double-helical DNA by (T,G)-containing oligonucleotides in the presence of a triple helix-specific ligand.
abstract: Triple helix formation requires a polypurine- polypyrimidine sequence in the target DNA. Recent works have shown that this constraint can be circumvented by using alternate strand triplex-forming oligonucleotides. We have previously demonstrated that (T,G)-containing triplex- forming oligonucleotides may adopt a parallel or an antiparallel orientation with respect to an oligopurine target, depending upon the sequence and, in particular, upon the number of 5'-GpT-3' and 5'-TpG-3' steps [Sun et al. (1991) C.R. Acad. Sci. Paris Ser III, 313, 585-590]. A single (T,G)-containing oligonucleotide can therefore interact with two oligopurine stretches which alternate on the two strands of the target DNA. The (T,G) switch oligonucleotide contains a 5'-part targeted to one of the oligopurine sequences in a parallel orientation followed by a 3'-part that adopts an antiparallel orientation with respect to the second oligopurine sequence. We show that a limitation to the stability of such a triplex may arise from the instability of the antiparallel part, composed of reverse-Hoogsteen C.GxG and T.AxT base triplets. Using DNase I footprinting and ultraviolet absorption experiments, we report that a benzo[e]pyridoindole derivative [(3-methoxy- 7H-8-methyl-11-[(3'-amino-propyl) amino] benzo[e]pyrido [4,3-b]indole (BePI)], a drug interacting more tightly with a triplex than with a duplex DNA, strongly stabilizes triplexes with reverse-Hoogsteen C.GxG and T.AxT triplets thus allowing a stabilization of the triplex-forming switch (T,G) oligonucleotide on alternating oligopurine- oligopyrimidine 5'-(Pu)14(Py)14-3' duplex sequences. These results lead to an extension of the range of oligonucleotide sequences for alternate strand recognition of duplex DNA.
authors.affiliation: Laboratoire de Biophysique, CNRS URA 481, INSERM U 201, Paris, France.
authors.forename: T
authors.initials: T
authors.lastname: de Bizemont
authors.forename: G
authors.initials: G
authors.lastname: Duval-Valentin
authors.forename: J S
authors.initials: JS
authors.lastname: Sun
authors.forename: E
authors.initials: E
authors.lastname: Bisagni
authors.forename: T
authors.initials: T
authors.lastname: Garestier
authors.forename: C
authors.initials: C
authors.lastname: Hélène
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D004247:DNA / Q000737:chemistry* / Q000235:genetics; D007211:Indoles; D007364:Intercalating Agents; D008024:Ligands; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000737:chemistry* / Q000235:genetics; D011725:Pyridines
chemical_list: D007211:Indoles; D007364:Intercalating Agents; D008024:Ligands; D009841:Oligonucleotides; D011725:Pyridines; C082732:3-methoxy-7H-8-methyl-11-((3'-amino)propylamino)benzo(e)pyrido(4,3-b)indole; D004247:DNA