title: High-resolution structure of a DNA helix forming (C.G)*G base triplets.
abstract: Triple helices result from interaction between single- and double-stranded nucleic acids. Their formation is a possible mechanism for recombination of homologous gene sequences in nature and provides, inter alia, a basis for artificial control of gene activity. Triple-helix motifs have been extensively studied by a variety of techniques, but few high-resolution structural data are available. The only triplet structures characterized so far by X-ray diffraction were in protein-DNA complexes studied at about 3 A resolution. We report here the X-ray analysis of a DNA nonamer, d(GCGAATTCG), to a resolution of 2.05 A, in which the extended crystal structure contains (C.G)*G triplets as a fragment of triple helix. The guanosine-containing chains are in a parallel orientation. This arrangement is a necessary feature of models for homologous recombination which results ultimately in replacement of one length of DNA by another of similar sequence. The present-structure agrees with many published predictions of triplex organization, and provides an accurate representation of an element that allows sequence-specific association between single- and double-stranded nucleic acids.
authors.affiliation: Department of Chemistry, Katholieke Universiteit Leuven, Heverlee, Belgium.
authors.forename: L
authors.initials: L
authors.lastname: Van Meervelt
authors.forename: D
authors.initials: D
authors.lastname: Vlieghe
authors.forename: A
authors.initials: A
authors.lastname: Dautant
authors.forename: B
authors.initials: B
authors.lastname: Gallois
authors.forename: G
authors.initials: G
authors.lastname: Précigoux
authors.forename: O
authors.initials: O
authors.lastname: Kennard
mesh_terms: D001483:Base Sequence; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*
chemical_list: D009838:Oligodeoxyribonucleotides; C093093:d(GCGAATTCG)