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Single-molecule Manipulation of G-quadruplexes by Magnetic Tweezers
Published on: September 19, 2017
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Spectroscopic Characterization of Mitochondrial G-Quadruplexes
Sara Illodo1,2, Cibrán Pérez-González1,2, Ramiro Barcia3
1Departamento de Química Física, Facultade de Ciencias, Universidade de Santiago de Compostela, 27002 Lugo, Spain.
International Journal of Molecular Sciences
|January 21, 2022
Summary
Guanine quadruplexes (G4s) in mitochondrial DNA are key to replication. This study reveals that specific G4 structures, particularly those from abundant G6AG7/G8 sequences, are more stable and form parallel topologies influenced by cations.
Area of Science:
- Molecular Biology
- Genetics
- Biophysics
Background:
- Guanine quadruplexes (G4s) are polymorphic nucleic acid structures crucial for biological processes.
- The discovery of G4s in mitochondrial DNA, especially within the conserved sequence block II (CSB II), is significant for understanding DNA replication.
- CSB II is known to form various G4 structures implicated in mitochondrial DNA replication.
Purpose of the Study:
- To identify and characterize the predominant G4 structures within the mitochondrial DNA CSB II region.
- To investigate the stability and topology of different G4 structures formed by varying guanine-rich sequences in CSB II.
- To explore the influence of cations on the formation and structural transitions of these G4s.
Main Methods:
- Bioinformatics analysis to identify G4-forming sequences within CSB II.
- Circular dichroism spectroscopy to determine G4 conformation and topology.
- Gel electrophoresis and fluorescence spectroscopy to assess G4 stability and cation-induced structural changes.
Main Results:
- Identified three main G4 structures in CSB II: RNA G4, DNA G4, and DNA:RNA hybrid G4.
- More abundant sequences (G6AG7 and G6AG8) form more stable G4s than less abundant ones (G5AG7).
- Parallel G4s are formed, with cation-dependent transitions from less ordered to highly ordered structures.
Conclusions:
- The stability and formation of G4s in CSB II are sequence-dependent, with longer G-runs yielding more stable structures.
- Cations like potassium and sodium play a critical role in stabilizing and ordering G4 topologies.
- These findings enhance our understanding of G4 structures in mitochondrial DNA and their potential role in replication.
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