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Structural polymorphism of telomeric DNA regulated by pH and divalent cation
Daisuke Miyoshi1, Shizuka Matsumura, Wei Li
1Department of Chemistry, Faculty of Science and Engineering, Konan University, Higashinada-ku, Kobe, Japan.
Nucleosides, Nucleotides & Nucleic Acids
|May 15, 2003
Summary
pH and cations regulate DNA structure, influencing G-quadruplex and I-motif formation over duplexes. This conformational switching is vital for biological processes involving guanine-rich and cytosine-rich DNA sequences.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- DNA oligonucleotides can form various multi-stranded structures, including duplexes, triplexes, and quadruplexes.
- Guanine-rich and cytosine-rich sequences, found in biologically significant regions like telomeres and centromeres, can form G-quadruplex and I-motif structures.
Purpose of the Study:
- To investigate the effects of pH and cations on the structure and stability of specific DNA oligonucleotides (d(G4T4G4) and d(C4A4C4)).
- To understand how environmental factors regulate conformational switching between different DNA structures.
Main Methods:
- Circular Dichroism (CD) spectroscopy to analyze DNA structures.
- Thermal melting curves to assess DNA stability.
- Isothermal Titration Calorimetry (ITC) to quantify duplex formation.
Main Results:
- Acidic conditions promote a stable I-motif structure in d(C4A4C4) but do not affect d(G4T4G4) G-quadruplex stability.
- Acidic conditions and calcium ions (Ca2+) inhibit duplex formation between d(G4T4G4) and d(C4A4C4).
- Ca2+ induces a parallel G-quadruplex structure in d(G4T4G4).
Conclusions:
- Both pH and cations play crucial roles in inducing and regulating structural polymorphism in DNA oligonucleotides.
- Environmental factors control conformational switching between duplex, G-quadruplex, and I-motif structures.
- These findings highlight the importance of pH and cations in regulating DNA structure and function in vivo.