Guanine Substitutions Prevent Conformational Switch from Antiparallel to Parallel G-Quadruplex

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Guanine quadruplexes (G4s) are non-canonical nucleic acid structures with diverse conformations.
• Cellular conditions, like crowding and dehydration, can influence G4 structure.
• Understanding G4 conformational flexibility is crucial for their biological roles.

Purpose of the Study:

• To investigate the effect of guanine substitutions on G4 conformational switching.
• To determine how cellular conditions and ligands affect G4 conformation.
• To assess the impact of substitution-induced conformational changes on G4 interactions.

Main Methods:

• Spectroscopic techniques were employed to analyze G4 structures.
• Dehydrating agents were used to induce conformational changes.
• Ligands like N-methyl mesoporphyrin IX were used to probe G4 interactions.

Main Results:

• Most guanine substitutions inhibit the switch from antiparallel/hybrid to parallel G4 forms under dehydration.
• The inhibition depends on the type of guanine substitution and its destabilizing potential, not its position.
• Ligand-induced parallel G4 formation can also be inhibited by guanine substitutions.

Conclusions:

• Guanine substitutions significantly restrict G4 conformational plasticity.
• The ability of G4s to switch conformations is sensitive to both sequence modifications and environmental factors.
• These findings have implications for understanding G4 function and interactions in vivo.