title: A novel chair-type G-quadruplex formed by a Bombyx mori telomeric sequence.
abstract: Recently, the human telomeric d[TAGGG(TTAGGG)(3)] sequence has been shown to form in K(+) solution an intramolecular (3+1) G-quadruplex structure, whose G-tetrad core contains three strands oriented in one direction and the fourth in the opposite direction. Here we present a study on the structure of the Bombyx mori telomeric d[TAGG(TTAGG)(3)] sequence, which differs from the human counterpart only by one G deletion in each repeat. We found that this sequence adopted multiple G-quadruplex structures in K(+) solution. We have favored a major G-quadruplex form by a judicious U-for-T substitution in the sequence and determined the folding topology of this form. We showed by NMR that this was a new chair-type intramolecular G-quadruplex which involved a two-layer antiparallel G-tetrad core and three edgewise loops. Our result highlights the effect of G-tract length on the folding topology of G-quadruplexes, but also poses the question of whether a similar chair-type G-quadruplex fold exists in the human telomeric sequences.
authors.affiliation: Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371.
authors.forename: Samir
authors.initials: S
authors.lastname: Amrane
authors.forename: Rita Wan Lin
authors.initials: RW
authors.lastname: Ang
authors.forename: Zhong Ming
authors.initials: ZM
authors.lastname: Tan
authors.forename: Chun
authors.initials: C
authors.lastname: Li
authors.forename: Joefina Kim Cheow
authors.initials: JK
authors.lastname: Lim
authors.forename: Jocelyn Mei Wen
authors.initials: JM
authors.lastname: Lim
authors.forename: Kah Wai
authors.initials: KW
authors.lastname: Lim
authors.forename: Anh Tuân
authors.initials: AT
authors.lastname: Phan
mesh_terms: D000818:Animals; D001483:Base Sequence; D012831:Bombyx / Q000235:genetics*; D002942:Circular Dichroism; D054856:G-Quadruplexes; D008958:Models, Molecular; D009038:Motion; D019906:Nuclear Magnetic Resonance, Biomolecular; D013056:Spectrophotometry, Ultraviolet; D016615:Telomere / Q000737:chemistry*