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The GTm6AC sequence is overwound and bent.
G V Fazakerley1, J Gabarro-Arpa, M Lebret
1Département de Biologie, Centre d'Etudes Nucléaires de Saclay, Gif-sur-Yvette, France.
Nucleic Acids Research
|April 11, 1989
Summary
Methylation of adenine in DNA (d(CGCGTm6ACGCG)) induces significant structural changes, causing helix bending. These alterations may explain why the T-m6A sequence is absent in natural DNA structures.
Area of Science:
- Molecular Biology
- Structural Biology
- Biochemistry
Background:
- DNA structure is crucial for its biological functions.
- Modified nucleobases can alter DNA conformation and properties.
- Understanding DNA structure provides insights into genetic processes.
Purpose of the Study:
- To determine the three-dimensional structure of the self-complementary decanucleotide d(CGCGTm6ACGCG).
- To investigate the conformational changes induced by adenine methylation at the T-m6A site.
- To elucidate the structural basis for the potential absence of T-m6A sequences in natural DNA.
Main Methods:
- Nuclear Magnetic Resonance (NMR) spectroscopy to obtain distance constraints.
- Molecular mechanics calculations to model the DNA structure.
- Analysis of helical parameters like twist and wedge roll angle.
Main Results:
- The three-dimensional structure of d(CGCGTm6ACGCG) was determined.
- Adenine methylation (m6A) induced significant conformational changes compared to B-DNA.
- Close proximity of methyl groups in the large groove caused steric hindrance.
- A helical twist of 45 degrees and a high negative wedge roll angle were observed between T.m6A base pairs.
- The helix exhibited a non-zero wedge roll, indicating bending.
Conclusions:
- Methylation of adenine at the T-m6A site significantly distorts DNA structure.
- Steric constraints from methyl groups lead to helix bending.
- These structural alterations provide a potential explanation for the rarity of T-m6A sequences in natural DNA.