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Studying the Potassium-Induced G‑Quadruplex DNA Folding Process Using Microscale Thermophoresis

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journal contribution
posted on 09.09.2019, 19:35 by Ming-Li Zhang, Ya-Peng Xu, Arvind Kumar, Yu Zhang, Wen-Qiang Wu
Guanine (G) quadruplexes (G4s) can be formed by G-rich sequences when stabilized by the binding of cations (typically K+ or Na+) and play an essential role in replication, recombination, transcription, and telomere maintenance. Understanding of the G4 folding process is crucial for determining their cellular functions. However, G4–K+ interactions and folding pathways are still not well understood. By using human telomeric G4 (hTG4) as an example, two binding states corresponding to two K+ cations binding to hTG4 were distinguished clearly and fitted precisely. The basic binding parameters during G4–K+ interactions were measured and calculated by taking advantage of microscale thermophoresis (MST), which monitors the changes in charge and size at the same time. The G-hairpin and G-triplex have been suggested as intermediates during G4 folding and unfolding. We further analyzed the equilibrium dissociation constants of 10 possible folding intermediates using MST; thus, the energetically favorable folding/unfolding pathways were proposed. The results might not only shed new light on G4–K+ interactions and G4 folding pathways but also provide an example for experimentally studying DNA–ion interactions.