Stability and structure of long intramolecular G-quadruplexes

Area of Science:

• Molecular Biology
• Biophysics
• Genetics

Background:

• G-quadruplexes are guanine-rich DNA/RNA structures crucial for cellular processes like transcription.
• Understanding G-quadruplex structure and stability aids in predicting in vivo formation and biological roles.
• Research has focused on isolated G-quadruplexes, with limited investigation into their interactions.

Purpose of the Study:

• To investigate the folding and stability of long DNA sequences forming two simultaneous G-quadruplexes.
• To compare the behavior of wild-type sequences with mutated versions designed for single G-quadruplex formation.
• To elucidate the folding model for multiple G-quadruplexes in long DNA strands.

Main Methods:

• Non-denaturing gel electrophoresis
• UV melting analysis
• Circular dichroism spectroscopy

Main Results:

• Long DNA sequences formed up to two distinct G-quadruplex structures.
• Coexistence of folded states with three or six stacked G-quartets was observed, influenced by the linker length (n).
• Thermodynamic stability remained constant for n > 3, supporting independent folding of adjacent G-quadruplexes.

Conclusions:

• Long G-quadruplex sequences exhibit complex folding patterns with multiple stable states.
• A 'beads-on-a-string' model accurately describes the independent folding of adjacent G-quadruplexes.
• Findings advance the understanding of G-quadruplex interactions and their biological implications.