title: A tetrahelical DNA fold adopted by tandem repeats of alternating GGG and GCG tracts.
abstract: DNA can form diverse higher-order structures, whose details are greatly dependent on nucleotide sequence. G-rich sequences containing four or more repeats of three guanines are expected to form G-quadruplexes. Here we show that DNA sequences with GGGAGCG repeats found in the regulatory region of the PLEKHG3 gene are capable of forming tetrahelical DNA structures that are distinct from G-quadruplexes. The d(GGGAGCGAGGGAGCG) sequence, VK1, forms a dimer. Two VK1 sequences connected by an adenine residue, VK2, fold into a monomer, which shares identical structural characteristics with the VK1 fold. Their four-stranded architectures are stabilized by four G-C, four G-A and six G-G base pairs. No G-quartets or Hoogsteen-type hydrogen-bonded guanine residues are present and the overall topology is conserved in the presence of Li(+), Na(+), K(+) and NH4(+) ions. Unique structural features include two edgewise loops on each side of the structure stabilized by three G-G base pairs in N1-carbonyl symmetric geometry.
authors.affiliation: Slovenian NMR Centre, National Institute of Chemistry, SI-1000 Ljubljana, Slovenia.
authors.forename: Vojč
authors.initials: V
authors.lastname: Kocman
authors.affiliation: 1] Slovenian NMR Centre, National Institute of Chemistry, SI-1000 Ljubljana, Slovenia [2] EN-FIST Centre of Excellence, SI-1000 Ljubljana, Slovenia [3] Faculty of Chemistry and Chemical Technology, University of Ljubljana, SI-1000 Ljubljana, Slovenia.
authors.forename: Janez
authors.initials: J
authors.lastname: Plavec
mesh_terms: D020029:Base Pairing; D001483:Base Sequence; D002247:Carbon Isotopes; D002414:Cations, Monovalent; D004247:DNA / Q000737:chemistry*; D019281:Dimerization; D054856:G-Quadruplexes; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009587:Nitrogen Isotopes; D009841:Oligonucleotides / Q000737:chemistry*; D011068:Poly G / Q000737:chemistry*; D020080:Tandem Repeat Sequences
chemical_list: D002247:Carbon Isotopes; D002414:Cations, Monovalent; D020662:Guanine Nucleotide Exchange Factors; D009587:Nitrogen Isotopes; D009841:Oligonucleotides; D011068:Poly G; D004247:DNA