NMR studies on truncated sequences of human telomeric DNA: observation of a novel A-tetrad

Nucleic Acids Res. 1999 Oct 1;27(19):3836-43. doi: 10.1093/nar/27.19.3836.


The structure of the telomeric DNA has been a subject of extensive investigation in recent years due to the realization that it has important functional roles to play in vivo and the observations that truncated telomeric sequences exhibit a great variety of 3D structures in aqueous solutions. In this context, we describe here NMR structural studies on two truncated human telomeric DNA sequences, d-AG(3)T and d-TAG(3)T in solutions containing K(+)ions. The G(3)stretches in both the oligonucleotides were seen to form parallel-stranded quadruplexes. However, the AG(3)segment as a whole, had different structural characteristics. The structure of d-AG(3)T revealed the formation of a novel A-tetrad, which was not seen in d-TAG(3)T. The A's in the tetrad had syn glycosidic conformation as opposed to the anti conformation of the G's in the G-tetrads. The A-tetrad stacked well over the adjacent G-tetrad and the twist angle at this step was smaller in d-AG(3)T than in d-TAG(3)T. These observations are expected to be significant from the point of view of structural diversity and recognition in telomeres.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • DNA / chemistry*
  • Humans
  • Nuclear Magnetic Resonance, Biomolecular
  • Nucleic Acid Conformation
  • Oligodeoxyribonucleotides / chemistry
  • Telomere*


  • Oligodeoxyribonucleotides
  • DNA