A novel chair-type G-quadruplex formed by a Bombyx mori telomeric sequence |
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Authors: | Samir Amrane Rita Wan Lin Ang Zhong Ming Tan Chun Li Joefina Kim Cheow Lim Jocelyn Mei Wen Lim Kah Wai Lim and Anh Tun Phan |
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Institution: | Samir Amrane, Rita Wan Lin Ang, Zhong Ming Tan, Chun Li, Joefina Kim Cheow Lim, Jocelyn Mei Wen Lim, Kah Wai Lim, and Anh Tuân Phan |
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Abstract: | Recently, the human telomeric dTAGGG(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 dTAGG(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. |
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