Solution structures of multiple G-quadruplex complexes induced by a platinum(II)-based tripod reveal dynamic binding

Wenting Liu,Liu-Yi Liu,Danzhou Yang,Wenjuan Zeng,Zong-Wan Mao,Yi-Fang Zhong,Chu-Tong Shen,Fuyi Wang

doi:10.1038/s41467-018-05810-4

Abstract

DNA G-quadruplexes are not only attractive drug targets for cancer therapeutics, but also have important applications in supramolecular assembly. Here, we report a platinum(II)-based tripod (Pt-tripod) specifically binds the biological relevant hybrid-1 human telomeric G-quadruplex (Tel26), and strongly inhibits telomerase activity. Further investigations illustrate Pt-tripod induces the formation of monomeric and multimeric Pt-tripod‒Tel26 complex structures in solution. We solve the 1:1 and the unique dimeric 4:2 Pt-tripod–Tel26 complex structures by NMR. The structures indicate preferential binding of Pt-tripod to the 5ʹ-end of Tel26 at a low Pt-tripod/Tel26 ratio of 0–1.0. After adding more Pt-tripod, the Pt-tripod binds the 3ʹ-end of Tel26, unexpectedly inducing a unique dimeric 4:2 structure interlocked by an A:A non-canonical pair at the 3ʹ-end. Our structures provide a structural basis for understanding the dynamic binding of small molecules with G-quadruplex and DNA damage mechanisms, and insights into the recognition and assembly of higher-order G-quadruplexes.

Highlights

DNA G-quadruplexes are attractive drug targets for cancer therapeutics, and have important applications in supramolecular assembly
We demonstrate the Pt-tripod induces the formation of multiple Pt-tripod–G-quadruplex complex structures, including monomeric, dimeric, and multimeric complex structures, by NMR, ESI-MS, native polyacrylamide gel electrophoresis (PAGE) and Fluorescence resonance energy transfer (FRET) melting experiments
This work provides structural information regarding the dynamic binding of the Pt-tripod with the hybrid-1 human telomeric G-quadruplex Tel[26] (Supplementary Movie 1)

Summary

Introduction

DNA G-quadruplexes are attractive drug targets for cancer therapeutics, and have important applications in supramolecular assembly. We report a platinum(II)based tripod (Pt-tripod) binds the biological relevant hybrid-1 human telomeric Gquadruplex (Tel26), and strongly inhibits telomerase activity. Previous studies in human cancer cells have demonstrated DNA G-quadruplex structure formation in telomeres[16], and G-quadruplex stabilization by small molecules[17] induces tumour cell senescence and apoptosis by repressing telomerase activity[18] and the DNA damage response pathway[19,20]. Structural information of higher-order G-quadruplex assemblies promoted by small molecules is essential for investigating the specific binding of biological relevant sequential G-quadruplexes in the long telomere. We find that the Pt-tripod binds to the biological relevant hybrid-1 human telomeric Gquadruplex DNA Tel[26] (Fig. 1b) and strongly repress telomerase activity. To understand the molecular mechanisms of multiple complexes induced by the Pt-tripod, solution NMR structures for the 1:1 and the dimeric 4:2 Pttripod–Tel[26] complexes are solved and presented, revealing the dynamic binding and detailed interaction of the Pt-tripod

Methods

Results

Conclusion