Inhibited complete folding of consecutive human telomeric G-quadruplexes

Area of Science:

• Molecular Biology
• Biophysics
• Genomics

Background:

• Noncanonical DNA structures called G-quadruplexes are vital in human DNA metabolism.
• The telomeric overhang region, associated with cancer and aging, contains G-rich repeats prone to G-quadruplex formation.
• Multiple consecutive G-quadruplexes can form in specific genomic regions.

Purpose of the Study:

• To investigate the folding dynamics of consecutive G-quadruplexes.
• To understand the influence of different ionic conditions (potassium and sodium) on G-quadruplex formation.
• To elucidate the factors inhibiting complete G-quadruplex folding.

Main Methods:

• Single-molecule Förster Resonance Energy Transfer (smFRET) spectroscopy
• Circular dichroism (CD) spectroscopy
• Thermal melting analysis
• Molecular dynamics (MD) simulations

Main Results:

• Observed coexistence of partially and fully folded DNA structures, including consecutive G-quadruplexes.
• Demonstrated fast G-quadruplex folding but slow thermodynamic equilibrium establishment in sodium buffers.
• Identified inhibition of full consecutive G-quadruplex formation by off-path DNA conformations.

Conclusions:

• Consecutive G-quadruplex formation can be described by a unified model under non-equilibrium and equilibrium conditions.
• The numerous possible DNA conformations can hinder the achievement of fully folded consecutive G-quadruplex structures.
• Understanding these folding pathways is crucial for G-quadruplex-related biological processes.