title: DNA octaplex formation with an I-motif of water-mediated A-quartets: reinterpretation of the crystal structure of d(GCGAAAGC).
abstract: The crystal structure of the tetragonal form of d(gcGAAAgc) has been revised and reasonably refined including the disordered residues. The two DNA strands form a base-intercalated duplex, and the four duplexes are assembled according to the crystallographic 222 symmetry to form an octaplex. In the central region, the eight strands are associated by I-motif of double A-quartets. Furthermore, eight hydrated-magnesium cations link the four duplexes to support the octaplex formation. Based on these structural features, a proposal that folding of d(GAAA)n, found in the non-coding region of genomes, into an octaplex can induce slippage during replication to facilitate length polymorphism is presented.
authors.affiliation: Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuda, Midori-ku, Yokohama 226-850.
authors.forename: Yoshiteru
authors.initials: Y
authors.lastname: Sato
authors.forename: Kenta
authors.initials: K
authors.lastname: Mitomi
authors.forename: Tomoko
authors.initials: T
authors.lastname: Sunami
authors.forename: Jiro
authors.initials: J
authors.lastname: Kondo
authors.forename: Akio
authors.initials: A
authors.lastname: Takénaka
mesh_terms: D020029:Base Pairing; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry*; D018598:Minisatellite Repeats; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D009838:Oligodeoxyribonucleotides; D014867:Water; D004247:DNA