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Structural polymorphism of telomere DNA: interquadruplex and duplex-quadruplex conversions probed by Raman
1Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri, Kansas City 64110-2499.
Biochemistry
|June 28, 1994
Summary
Oxytricha nova telomeric DNA exhibits structural polymorphism. Alkali metal ions like sodium (Na+) and potassium (K+) control transitions between different DNA structures, including duplex and quadruplex forms.
Area of Science:
- Biochemistry
- Molecular Biology
- Spectroscopy
Background:
- Telomeric DNA sequences are crucial for maintaining chromosome stability.
- Oxytricha nova telomeres are known for their unique G-rich sequences and potential for G-quadruplex formation.
Purpose of the Study:
- To elucidate the solution secondary structures and nucleotide conformations of Oxytricha nova telomeric DNA.
- To investigate the structural polymorphism and cation-dependent transitions in telomeric DNA models.
Main Methods:
- Raman spectroscopy was employed to analyze DNA structures in solution.
- Studies utilized synthetic DNA models: single-stranded [d(T4G4)4] and double-stranded [d(G4T4G4).d(C4A4C4)].
Main Results:
- Demonstrated structural polymorphism in both single-stranded and double-stranded telomere models.
- Identified an interquadruplex equilibrium in d(T4G4)4 controlled by Na+ and K+ concentrations, with distinct dG sugar conformations in parallel and antiparallel forms.
- Showed reversible duplex-quadruplex conversion in d(G4T4G4).d(C4A4C4) at high cation concentrations.
Conclusions:
- Oxytricha telomeric DNA structure is highly polymorphic and sensitive to alkali cations.
- Conversions between duplex and quadruplex forms are regulated by an alkali cation switch mechanism.