Stability of human telomere quadruplexes at high DNA concentrations

Area of Science:

• Biophysics
• Molecular Biology
• Supramolecular Chemistry

Background:

• Macromolecular crowding is crucial for mimicking cellular environments and understanding DNA quadruplex stability.
• Polyethylene glycol (PEG) is commonly used as a crowding agent, increasing thermal and thermodynamic stability of DNA quadruplexes at micromolar concentrations.

Purpose of the Study:

• To investigate the effect of using DNA G-quadruplexes themselves as crowding agents.
• To determine how self-association of G-quadruplexes influences their stability and folding topology at high concentrations.

Main Methods:

• Thermal stability assays were performed on DNA G-quadruplexes at concentrations ranging from 3 µM to 9 mM.
• Thermodynamic stability (ΔG°37) was evaluated at concentrations below 2 mM.
• Changes in folding topology were analyzed at high DNA concentrations (2-9 mM).

Main Results:

• Thermostability remained unchanged up to ~2 mM G-quadruplex concentration, then increased, indicating non-monomolecular unfolding units.
• Self-association of G-quadruplexes was observed above ~2 mM.
• Folding topology shifted from antiparallel to hybrid, and then to parallel quadruplexes at 6-9 mM concentrations.
• ΔG°37 values slightly increased below 2 mM, unlike the effect of non-DNA crowders.

Conclusions:

• DNA G-quadruplexes exhibit distinct self-crowding behavior compared to external agents like PEG.
• High concentrations promote G-quadruplex self-association and topological transitions, influenced by volume exclusion and counterion screening.
• The findings provide insights into the complex behavior of DNA structures in crowded biological environments.