Modelling studies on neurodegenerative disease-causing triplet repeat sequences d(GGC/GCC)n and d(CAG/CTG)n

Area of Science:

• Molecular Biology
• Biophysics
• Computational Chemistry

Background:

• Triplet repeat expansion diseases are linked to specific DNA sequences.
• Understanding the structural dynamics of these sequences is crucial for disease mechanism insights.

Purpose of the Study:

• To investigate potential DNA structures formed by d(GGC/GCC)5 and d(CAG/CTG)5 sequences.
• To evaluate the energetic favorability of these structures using molecular mechanics.
• To correlate structural findings with biological function and disease association.

Main Methods:

• Utilized model building to propose potential DNA structures.
• Employed molecular mechanics to study the stability and energy of proposed structures.
• Analyzed DNA structures under varying salt conditions.

Main Results:

• Identified potential hairpin and quadruplex structures for the repeat sequences.
• Demonstrated that hairpin and hairpin dimer structures are energetically favorable, comparable to B-DNA duplexes.
• Found Greek key quadruplex structures to be energetically comparable to hairpin dimers and B-DNA duplexes at high salt concentrations.
• Observed favorable base stacking in quadruplex structures and cyclic hydrogen bonding in non-G tetrads of minimized structures.

Conclusions:

• DNA hairpin and quadruplex structures are plausible for d(GGC/GCC)5 and d(CAG/CTG)5 sequences.
• These structures exhibit significant energetic stability, rivaling conventional DNA duplexes.
• The findings provide structural insights into the potential mechanisms underlying triplet repeat expansion diseases.