Sugar Puckering Drives G-Quadruplex Refolding: Implications for V-Shaped Loops

Area of Science:

• Biochemistry
• Structural Biology
• Nucleic Acid Chemistry

Background:

• DNA G-quadruplexes are four-stranded nucleic acid structures with diverse biological roles.
• The (3+1) hybrid structure is one known topology adopted by G-quadruplexes.
• Modifications to G-quadruplex structures can alter their topology and properties.

Purpose of the Study:

• To investigate the impact of specific nucleotide analogues on G-quadruplex structure.
• To explore the formation of V-shaped loops in modified G-quadruplexes.
• To understand the role of sugar conformation in G-quadruplex folding.

Main Methods:

• Chemical synthesis of modified G-quadruplex sequences.
• Structural analysis using techniques like NMR spectroscopy (implied).
• Comparative analysis of different nucleotide analogues (2'-deoxy-2'-fluoro-riboguanosine, riboguanosine, 2'-F-arabinoguanosine).

Main Results:

• Introduction of 2'-deoxy-2'-fluoro-riboguanosine analogues promoted a switch to a V-loop topology.
• The V-loop formation involved a 5'-terminal G residue in the central tetrad and a zero-nucleotide loop.
• One modified analogue adopted an unfavored syn conformation, indicating sugar pucker's dominance.
• Riboguanosine substitutions also supported V-loop formation.
• 2'-F-arabinoguanosine analogues did not support V-loop formation due to their sugar conformation.

Conclusions:

• Sugar pucker plays a critical role in stabilizing the V-loop topology in G-quadruplexes.
• The propensity of nucleotide analogues to adopt specific sugar conformations dictates their ability to form V-loops.
• This study provides insights into the structural plasticity of G-quadruplexes and the influence of chemical modifications.