Ligand-Induced Dimerization of a Truncated Parallel MYC G-Quadruplex

Area of Science:

• Biochemistry
• Molecular Biology
• Chemical Biology

Background:

• The MYC gene promoter contains a G-rich sequence that can form a DNA quadruplex (G4).
• DNA quadruplexes are unique secondary structures with potential applications in nanotechnology and therapeutics.
• Understanding ligand interactions with G4 structures is crucial for developing G4-based technologies.

Purpose of the Study:

• To investigate the binding mechanism of an indoloquinoline derivative with an aminoalkyl side chain to the MYC3 DNA quadruplex.
• To elucidate the structural consequences of this ligand-G4 interaction.
• To explore the potential of ligand-induced G4 dimerization for technological applications.

Main Methods:

• Isothermal titration calorimetry (ITC) to study binding thermodynamics.
• Electrophoretic mobility shift assays (EMSA) to assess structural changes.
• Nuclear Magnetic Resonance (NMR) spectroscopy to confirm structural details.

Main Results:

• The indoloquinoline derivative binds to the MYC3 quadruplex, forming a 1:2 ligand/quadruplex complex.
• Ligand binding induces dimerization of the MYC3 quadruplex, with the ligand intercalated between two quadruplex units.
• Excess ligand molecules bind to the 5'-outer tetrads of the dimer.

Conclusions:

• The indoloquinoline derivative acts as a molecular 'staple' to promote MYC3 G4 dimerization.
• Ligand-promoted G4 dimerization provides a mechanism for controlled assembly/disassembly of G4 structures.
• This finding expands the toolkit for quadruplex-based technologies and molecular assembly.