title: Stability and structure of telomeric DNA sequences forming quadruplexes containing four G-tetrads with different topological arrangements.
abstract: Telomeres are DNA-protein structures at the ends of eukaryotic chromosomes, the DNA of which comprise noncoding repeats of guanine-rich sequences. Telomeric DNA plays a fundamental role in protecting the cell from recombination and degradation. Telomeric sequences can form quadruplex structures stabilized by guanine quartets. These structures can be constructed from one, two, or four oligonucleotidic strands. Here, we report the thermodynamic characterization of the stability, analyzed by differential scanning calorimetry, of three DNA quadruplexes of different molecularity, all containing four G-tetrads. The conformational properties of these quadruple helices were studied by circular dichroism. The investigated oligomers form well-defined G-quadruplex structures in the presence of sodium ions. Two have the truncated telomeric sequence from Oxytricha, d(TGGGGT) and d(GGGGTTTTGGGG), which form a tetramolecular and bimolecular quadruplex, respectively. The third sequence, d(GGGGTTGGGGTGTGGGGTTGGGG) was designed to form a unimolecular quadruplex. The thermodynamic parameters of these quadruplexes have been determined. The tetramolecular structure is thermodynamically more stable than the bimolecular one, which, in turn, is more stable than the unimolecular one. The experimental data were discussed in light of the molecular-modeling study.
authors.affiliation: Dipartimento di Chimica, Via Cintia, Università Federico II di Napoli, 80126, Naples, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Petraccone
authors.forename: Eva
authors.initials: E
authors.lastname: Erra
authors.forename: Veronica
authors.initials: V
authors.lastname: Esposito
authors.forename: Antonio
authors.initials: A
authors.lastname: Randazzo
authors.forename: Luciano
authors.initials: L
authors.lastname: Mayol
authors.forename: Lucia
authors.initials: L
authors.lastname: Nasti
authors.forename: Guido
authors.initials: G
authors.lastname: Barone
authors.forename: Concetta
authors.initials: C
authors.lastname: Giancola
mesh_terms: D001483:Base Sequence; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D004247:DNA / Q000138:chemical synthesis / Q000737:chemistry*; D054856:G-Quadruplexes; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D009841:Oligonucleotides / Q000138:chemical synthesis; D016615:Telomere / Q000737:chemistry* / Q000235:genetics; D013816:Thermodynamics
chemical_list: D009841:Oligonucleotides; D004247:DNA