Theoretical modelling of epigenetically modified DNA sequences

Area of Science:

• Computational chemistry
• Molecular biology
• Epigenetics

Background:

• Epigenetic modifications alter DNA structure and function.
• Understanding these structural changes is crucial for biological processes.

Purpose of the Study:

• To investigate the structural impact of epigenetic modifications on DNA.
• To evaluate computational methods for modeling these effects.

Main Methods:

• Density functional theory (DFT) calculations for base pairs and trimers.
• Molecular mechanics (MM) and hybrid QM/MM simulations.
• Inclusion of DNA backbone, counterions, and solvation in models.

Main Results:

• Cytosine modifications (methyl, hydroxymethyl, formyl, carboxy) minimally affect CG base pair geometry.
• Larger structural changes observed in trimers and heptamers, including base pair angles and step parameters.
• QM/MM methods with extensive QM regions accurately reproduce DFT structures.

Conclusions:

• Epigenetic modifications induce context-dependent structural changes in DNA.
• Accurate modeling requires realistic molecular contexts, including the backbone and solvent.
• Validated QM/MM methods serve as benchmarks for larger DNA systems.