Stability of G,A triple helices

Area of Science:

• Molecular Biology
• Biophysics
• Computational Chemistry

Background:

• DNA triplexes are crucial for various biological processes and therapeutic applications.
• Understanding the sequence-stability relationship in DNA triplexes is essential for their design and utilization.
• Previous studies have explored factors influencing DNA triplex stability, but sequence selection and ion effects require further investigation.

Purpose of the Study:

• To select double-stranded DNA sequences that form stable triplexes with purine oligonucleotides at different temperatures.
• To elucidate the sequence rules governing triplex stability.
• To computationally investigate the role of metal ions in stabilizing DNA triplexes.

Main Methods:

• A double aptamer selection approach was employed to identify DNA sequences capable of forming stable triplexes.
• Cold exchange method was used to confirm the stability of selected triplexes.
• Density scaled Monte Carlo simulations were performed to analyze the ion environment around DNA triplexes.

Main Results:

• Selected DNA sequences exhibit high guanine (G) content.
• Triplex stability increases when G residues are arranged in stretches.
• Computer simulations revealed that magnesium ions (Mg2+) preferentially associate with G residues, forming a stabilizing 'spine', and are repelled by adenine (A) residues.

Conclusions:

• The study identified specific DNA sequence characteristics that promote stable triplex formation.
• Guanine-rich sequences, particularly with G-stretches, are favorable for triplex stability.
• Magnesium ion coordination plays a critical role in stabilizing DNA triplexes, with a specific binding pattern around guanine residues.