title: A comparison of the properties and the solution structure for RNA and DNA quadruplexes which contain two GGAGG sequences joined with a tetranucleotide linker.
abstract: We have determined solution structure of r(GGAGGUUUUGGAGG) (R14) by NMR; the RNA 14-mer forms an intra-strand parallel quadruplex with a G-tetrad and a hexad, in which a G-tetrad core is augmented by association of two A residues. The quadruplex further forms a dimer through stacking interaction between the hexads. In order to obtain insight into the difference between RNA and DNA quadruplexes, we synthesized the corresponding DNA 14-mer, d(GGAGGTTTTGGAGG) (D14), and examined its properties and structure by CD, gel electrophoresis, and NMR. K+ ions increased the thermal stability of both R14 and D14 structures. The binding affinity of K+ ions to R14 was much higher than that to D14. The CD and gel electrophoretic studies suggest that D14 forms a quadruplex entirely different from that of R14 in the presence of K+ ions; two molecules of D14 form a quadruplex with both antiparallel and parallel strand alignments and with diagonal loops at both ends of the stacked G-tetrads. The NMR study also gave results that are consistent with such structure: alternate glycosidic conformation, 5'G(syn)-G(anti)3', and characteristic chemical shift data observed for many quadruplexes containing diagonal TTTT loops.
authors.affiliation: Department of Environment and Natural Sciences, Graduate School of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan.
authors.forename: Hui
authors.initials: H
authors.lastname: Liu
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kugimiya
authors.forename: Tokuhiro
authors.initials: T
authors.lastname: Sakurai
authors.forename: Masato
authors.initials: M
authors.lastname: Katahira
authors.forename: Seiichi
authors.initials: S
authors.lastname: Uesugi
mesh_terms: D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D054856:G-Quadruplexes; D046911:Macromolecular Substances; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000737:chemistry; D011188:Potassium / Q000378:metabolism; D012313:RNA / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*; D012996:Solutions / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D046911:Macromolecular Substances; D009841:Oligonucleotides; D012996:Solutions; D012313:RNA; D004247:DNA; D011188:Potassium