A 4:1 stoichiometric binding and stabilization of mitoxantrone-parallel stranded G-quadruplex complex established by...

Area of Science:

• Biochemistry
• Molecular Biology
• Medicinal Chemistry

Background:

• Telomerase enzyme activity is a key cancer marker.
• Small molecule ligands stabilizing G-quadruplex structures inhibit telomerase.
• Understanding ligand-G-quadruplex binding is crucial for anti-cancer drug development.

Purpose of the Study:

• To investigate the interaction between the anti-tumor drug mitoxantrone (MTX) and a specific tetra-molecular parallel stranded G-quadruplex DNA sequence (d-TTGGGGT).
• To elucidate the binding mode and stoichiometry of mitoxantrone on the G-quadruplex structure.

Main Methods:

• UV-Vis absorbance spectroscopy
• Fluorescence spectroscopy
• Circular Dichroism (CD) spectroscopy
• Proton Nuclear Magnetic Resonance (NMR) spectroscopy
• Thermal melting studies

Main Results:

• Mitoxantrone binding induced significant changes in absorbance and fluorescence spectra, indicating complex formation.
• Spectroscopic data suggested a dual binding mode for mitoxantrone with two distinct binding sites.
• Circular Dichroism and NMR studies confirmed that mitoxantrone binds as stacked dimers.
• Thermal melting studies showed stabilization of the G-quadruplex structure upon mitoxantrone binding.

Conclusions:

• Mitoxantrone binds to the G-quadruplex DNA externally as two dimers (four molecules total) at two distinct sites.
• This specific binding mode provides valuable information for designing effective anti-cancer therapeutics targeting G-quadruplex structures.