156d
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REFINED SOLUTION STRUCTURE OF THE DIMERIC QUADRUPLEX FORMED FROM THE OXYTRICHA TELOMERIC OLIGONUCLEOTIDE D(GGGGTTTTGGGG)
OverviewOverview
BACKGROUND: Telomeres, the structures at the ends of linear eukaryotic, chromosomes, are essential for chromosome replication and stability. The, telomeres of the unicellular ciliate Oxytricha contain a 3' single strand, overhang composed of two repeats of the telomere repeat sequence, d(TTTTGGGG). It has been proposed that oligonucleotides containing this, repeat can form DNA quadruplexes via hydrogen bonding of the guanines into, quartets. Such structures may be relevant to the biological function of, the telomere, and in G-rich sequences elsewhere in the genome. RESULTS: We, have previously determined from solution NMR data that the Oxy-1.5, Oxytricha repeat oligonucleotide d(GGGGTTTTGGGG) dimerizes to form an, intermolecular quadruplex composed of four guanine quartets and with the, thymines in loops across the diagonal at opposite ends of the quadruplex., We report here the refined solution structure of Oxy-1.5. This structure, is compared with the previously published crystal structure of the same, oligonucleotide. CONCLUSIONS: Oxy-1.5 forms a well-defined, symmetrical, structure with ordered thymine loops. Both the solution and crystal, structures of Oxy-1.5 are quadruplexes with alternating syn and anti, glycosyl conformation of guanines along each strand of the helix and have, thymine loops at opposite ends. However, the topology of the two, structures is fundamentally different, leading to significant structural, differences. A topological pathway for the formation and interconversion, of the two structures is proposed.
About this StructureAbout this Structure
156D is a Protein complex structure of sequences from [1]. Full crystallographic information is available from OCA.
ReferenceReference
Refined solution structure of the dimeric quadruplex formed from the Oxytricha telomeric oligonucleotide d(GGGGTTTTGGGG)., Schultze P, Smith FW, Feigon J, Structure. 1994 Mar 15;2(3):221-33. PMID:8069635
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