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B-Z transition in methylated DNA. A quantum-chemical study
European Journal of Biochemistry
|April 15, 1983
Summary
Methylation significantly impacts DNA structure by altering rotation energies around the glycosidic bond. This explains the preference for Z-DNA forms in methylated DNA, crucial for understanding DNA transitions.
Area of Science:
- Quantum Chemistry
- Molecular Biology
- Biophysics
Background:
- Methylation is a key epigenetic modification influencing DNA structure and function.
- The B-Z DNA transition is a critical conformational change with implications for gene regulation.
Purpose of the Study:
- To investigate the effect of methylation on the energetics of glycosidic bond rotation in nucleosides.
- To correlate computational findings with experimental observations of Z-DNA formation.
Main Methods:
- Modified neglect of differential overlap (MNDO) quantum-chemical calculations were performed on nucleoside systems.
- Energetic barriers for anti-syn rotation around the glycosidic C(1')-N bond were calculated.
Main Results:
- Pyrimidine nucleosides (C, m5C) showed high anti-syn activation energy, while purine nucleosides (G, m6G, m7G, m8G) exhibited moderate barriers.
- Methylation of m5C and m8G enhanced anti-syn activation energy due to steric and electronic factors.
- Selective guanine methylation increased syn conformer stabilization, consistent with experimental B-Z transition data.
Conclusions:
- Methylation-induced changes in glycosidic bond rotation energies are critical for Z-DNA formation.
- Computational data supports the role of these rotations in the initiating steps of the B-Z DNA transition.
- Understanding these molecular mechanisms provides insight into DNA conformational dynamics and epigenetic regulation.