Divalent cations and molecular crowding buffers stabilize G-triplex at physiologically relevant temperatures

Area of Science:

• Structural Biology
• Biochemistry
• Molecular Biophysics

Background:

• G-triplexes are non-canonical DNA structures formed by G-rich sequences.
• Putative G-triplex-forming sequences are more common than G-quadruplex-forming sequences, yet research is limited.
• Understanding G-triplex stability is crucial for exploring their biological roles.

Purpose of the Study:

• To investigate the impact of molecular crowding on G-triplex formation and stability.
• To examine the effects of physiologically relevant metal ions (Na+, K+, Mg2+, Ca2+) on G-triplexes.
• To determine the conditions under which G-triplexes can form and remain stable at physiological temperatures.

Main Methods:

• Circular dichroism spectroscopy
• Thermodynamics analysis
• Optical tweezers measurements
• Calorimetry techniques

Main Results:

• Molecular crowding and the presence of Na+, K+, Mg2+, and Ca2+ ions promote G-triplex formation and enhance stability.
• Ca2+ exhibited the strongest stabilizing effect, followed by K+, Mg2+, and Na+.
• G-triplexes with three G-triads are stable above 37°C, particularly under molecular crowding and with K+ or Ca2+.

Conclusions:

• Molecular crowding and specific metal cations significantly stabilize G-triplex DNA structures.
• The findings suggest that stable G-triplexes can exist under physiological conditions.
• This study provides insights into the formation and stability of G-triplexes, highlighting their potential biological significance.