Crystal structures of a DNA octaplex with I-motif of G-quartets and its splitting into two quadruplexes suggest a folding mechanism of eight tandem repeats

Nucleic Acids Res. 2004 May 7;32(8):2541-9. doi: 10.1093/nar/gkh575. Print 2004.


Recent genomic analyses revealed many kinds of tandem repeats of specific sequences. Some of them are related to genetic diseases, but their biological functions and structures are still unknown. Two X-ray structures of a short DNA fragment d(gcGA[G]1Agc) show that four base-intercalated duplexes are assembled to form an octaplex at a low K+ concentration, in which the eight G5 residues form a stacked double G-quartet in the central part. At a higher K+ concentration, however, the octaplex is split into just two halves. These structural features suggest a folding process of eight tandem repeats of d(ccGA[G]4Agg), according to a double Greek-key motif. Such a packaging of the repeats could facilitate slippage of a certain sequence during DNA replication, to induce increase or decrease of the repeats.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Crystallography, X-Ray
  • DNA / chemistry*
  • DNA / genetics*
  • G-Quadruplexes
  • Minisatellite Repeats / genetics
  • Models, Molecular
  • Nucleic Acid Conformation* / drug effects
  • Potassium / metabolism
  • Potassium / pharmacology
  • Tandem Repeat Sequences / genetics*
  • Thermodynamics
  • Water / metabolism


  • Water
  • DNA
  • Potassium

Associated data

  • PDB/1V3N
  • PDB/1V3O
  • PDB/1V3P