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Single-Molecule Fluorescence Visualization of DNA Polymerase Dynamics at G-Quadruplexes
Published on: April 4, 2025
Structure and stability of a dimeric g-quadruplex formed by cyclic oligonucleotides
Joan Casals1, Júlia Viladoms, Enrique Pedroso
1Departament de Química Orgànica, Universitat de Barcelona, C/. Martí i Franquès 1, 08028 Barcelona, Spain.
Journal of Nucleic Acids
|August 21, 2010
Summary
Cyclic DNA structures can form stable quadruplexes. This study shows that cyclization of the human telomeric repeat does not prevent quadruplex formation, impacting its overall structure.
Area of Science:
- Biochemistry
- Structural Biology
- Nucleic Acid Chemistry
Background:
- The human telomeric repeat sequence (TTAGGG)n is known to form G-quadruplex structures.
- Cyclic DNA structures offer unique topological and stability properties compared to linear counterparts.
Purpose of the Study:
- To investigate the structural and stability characteristics of a cyclic dodecamer containing two human telomeric repeat units (d
). - To determine if phosphodiester chain cyclization influences G-quadruplex formation and topology.
Main Methods:
- Nuclear Magnetic Resonance (NMR) spectroscopy was employed to elucidate the three-dimensional structure.
- Melting temperature (Tm) analysis was used to assess the stability of the formed structure.
Main Results:
- In the presence of sodium ions, the cyclic dodecamer self-associates into a dimeric structure.
- This dimeric structure features a quadruplex formed by two macrocycles arranged in parallel, with three guanine tetrads connected by edgewise loops.
- The dimeric quadruplex structure exhibits a high melting temperature, indicating significant stability.
Conclusions:
- Cyclization of the phosphodiester backbone in DNA does not preclude the formation of G-quadruplex structures.
- While quadruplex formation is possible, the cyclic nature affects the global topology of the resulting structure compared to linear analogues.
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