Dual Binding of an Antibody and a Small Molecule Increases the Stability of TERRA G-Quadruplex.

Philip M. Yangyuoru,Shankar Balasubramanian,Giulia Biffi,Chiran Ghimire,Hanbin Mao,Marco Di Antonio

doi:10.1002/ange.201408113

Philip M. Yangyuoru, Shankar Balasubramanian + Show 4 more

Open Access

https://doi.org/10.1002/ange.201408113

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Abstract

In investigating the binding interactions between the human telomeric RNA (TERRA) G-quadruplex (GQ) and its ligands, it was found that the small molecule carboxypyridostatin (cPDS) and the GQ-selective antibody BG4 simultaneously bind the TERRA GQ. We previously showed that the overall binding affinity of BG4 for RNA GQs is not significantly affected in the presence of cPDS. However, single-molecule mechanical unfolding experiments revealed a population (48 %) with substantially increased mechanical and thermodynamic stability. Force-jump kinetic investigations suggested competitive binding of cPDS and BG4 to the TERRA GQ. Following this, the two bound ligands slowly rearrange, thereby leading to the minor population with increased stability. Given the relevance of G-quadruplexes in the regulation of biological processes, we anticipate that the unprecedented conformational rearrangement observed in the TERRA-GQ–ligand complex may inspire new strategies for the selective stabilization of G-quadruplexes in cells.

Highlights

In investigating the binding interactions between the human telomeric RNA (TERRA) G-quadruplex (GQ) and its ligands, it was found that the small molecule carboxypyridostatin and the GQ-selective antibody BG4 simultaneously bind the TERRA GQ
We recently demonstrated that RNA G-quadruplexes can form in the cytoplasm of cells and that they can be stabilized and visualized by the selective RNA GQ ligand carboxypyridostatin[15] and the antibody BG4.[16]. These observations have led to the possibility of a multifaceted regulatory approach, for example, through antibody–drug conjugates (ADCs).[17]
We investigated the dual binding of cPDS and the BG4 antibody to the TERRA G-quadruplex

Summary

Introduction

In investigating the binding interactions between the human telomeric RNA (TERRA) G-quadruplex (GQ) and its ligands, it was found that the small molecule carboxypyridostatin (cPDS) and the GQ-selective antibody BG4 simultaneously bind the TERRA GQ. Using a mechanical unfolding approach with laser tweezers, we found that a minor TERRA G-quadruplex population (48 %) has increased mechanical and thermodynamic stability when bound to both ligands.

Results

Conclusion