title: NMR studies on truncated sequences of human telomeric DNA: observation of a novel A-tetrad.
abstract: 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.
authors.affiliation: Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India.
authors.forename: P K
authors.initials: PK
authors.lastname: Patel
authors.forename: A S
authors.initials: AS
authors.lastname: Koti
authors.forename: R V
authors.initials: RV
authors.lastname: Hosur
mesh_terms: D004247:DNA / Q000737:chemistry*; D006801:Humans; D019906:Nuclear Magnetic Resonance, Biomolecular; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D016615:Telomere
chemical_list: D009838:Oligodeoxyribonucleotides; D004247:DNA