title: Structural polymorphism and thermal stability of telomere DNAs (T2G4)n and (T4G4)n.
abstract: The ends of eukaryotic chromosomes, termed telomeres, contain a single-stranded 3' overhang composed of tandemly repeated guanine-rich sequences, such as (T2G4)n and (T4G4)n, along one strand. The sequences can form defined folded tetraplex structures. Here we have systematically examined structural polymorphism and thermal stability of a series of oligonucleotide sequences, Tet n: (T2G4)n and Oxy n: (T4G4)n (n = 1, 2, 3, 4), using circular dichroism (CD) spectroscopy. The CD spectra of Tet 1 and Oxy 1 are consistent with those observed in tetraplex structures consisting of four parallel strands (type I conformation); whereas the spectra of Tet 2, Oxy 2, Oxy 3, and Oxy 4 correspond with those observed for tetraplex conformations where the strands are antiparallel (type II conformation). The spectra of Tet 3 and Tet 4 suggests that Tet 3 and Tet 4 can adopt both type I and type II conformations and they are structurally polymorphic. The melting temperatures of Tet n and Oxy n (n = 1, 2, 3, 4) measured by CD melting are consistent with the previously reported values obtained from differential scanning calorimetry (DSC). Furthermore, the CD melting of Tet 4 suggests that the type II conformation of Tet 4 changes into type I conformation between 55 degrees C and 70 degrees C.
authors.affiliation: Tsukuba Life Science Center, Institute of Physical and Chemical Research (RIKEN), Ibaraki, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Torigoe
authors.forename: M
authors.initials: M
authors.lastname: Kamiya
authors.forename: H
authors.initials: H
authors.lastname: Shindo
authors.forename: A
authors.initials: A
authors.lastname: Sarai
mesh_terms: D001483:Base Sequence; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry* / Q000235:genetics; D004355:Drug Stability; D006147:Guanine / Q000737:chemistry; D015394:Molecular Structure; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis / Q000737:chemistry / Q000235:genetics; D011110:Polymorphism, Genetic; D016615:Telomere / Q000737:chemistry* / Q000235:genetics; D013696:Temperature; D013941:Thymine / Q000737:chemistry
chemical_list: D009838:Oligodeoxyribonucleotides; D006147:Guanine; D004247:DNA; D013941:Thymine