Stability and structure of telomeric DNA sequences forming quadruplexes containing four G-tetrads with different topological arrangements.
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.
Petraccone
Luigi
L
Dipartimento di Chimica, Via Cintia, Università Federico II di Napoli, 80126, Naples, Italy.
Erra
Eva
E
Esposito
Veronica
V
Randazzo
Antonio
A
Mayol
Luciano
L
Nasti
Lucia
L
Barone
Guido
G
Giancola
Concetta
C
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
D009841:Oligonucleotides; D004247:DNA