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Publication Abstract from PubMed

Human telomeric guanine-rich DNA, which could adopt different G-quadruplex structures, plays important roles in protecting the cell from recombination and degradation. Although many of these structures were determined, the chair-type G-quadruplex structure remains elusive. Here, we present a crystal structure of the G-quadruplex composed of the human telomeric sequence d[GGGTTAGG8GTTAGGGTTAGG20G] with two dG to 8Br-dG substitutions at positions 8 and 20 with syn conformation in the K+ solution. It forms a novel three-layer chair-type G-quadruplex with two linking trinucleotide loops. Particularly, T5 and T17 are coplanar with two water molecules stacking on the G-tetrad layer in a sandwich-like mode through a coordinating K+ ion and an A6*A18 base pair. While a twisted Hoogsteen A12*T10 base pair caps on the top of G-tetrad core. The three linking TTA loops are edgewise and each DNA strand has two antiparallel adjacent strands. Our findings contribute to a deeper understanding and highlight the unique roles of loop and water molecule in the folding of the G-quadruplex.

The crystal structure of an antiparallel chair-type G-quadruplex formed by Bromo-substituted human telomeric DNA.,Geng Y, Liu C, Zhou B, Cai Q, Miao H, Shi X, Xu N, You Y, Fung CP, Din RU, Zhu G Nucleic Acids Res. 2019 Apr 8. pii: 5430838. doi: 10.1093/nar/gkz221. PMID:30957851^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.