A small molecule affecting the replication of trinucleotide repeat d(GAA)n.

Area of Science:

• Chemical synthesis and characterization of novel ligands.
• Biophysical chemistry and molecular interactions.
• DNA structure and polymerase inhibition.

Background:

• G-rich DNA sequences can form non-canonical structures like G-quadruplexes.
• Ligand binding to specific DNA structures is a key area in drug discovery.
• Understanding DNA-ligand interactions informs the development of novel therapeutic agents.

Purpose of the Study:

• To synthesize and characterize a new ligand, methylcarbamoylnaphthyridine dimer (MCND).
• To investigate the binding of MCND to the d(GAA)(n) DNA repeat sequence.
• To assess the effect of MCND binding on DNA polymerase activity.

Main Methods:

• Synthesis and characterization of MCND.
• UV thermal denaturation and circular dichroism spectroscopy for structural analysis.
• Surface plasmon resonance and mass spectrometry for binding kinetics and stoichiometry.
• Polymerase stop assays with Taq and human DNA polymerase alpha.

Main Results:

• MCND was successfully synthesized and characterized.
• MCND formed a stable hairpin structure with d(GAA)(n) repeats, with a 3:1 binding stoichiometry.
• The primary binding site was identified as the G-G mismatch within the AGA/AGA triad.
• MCND binding inhibited primer extension by both prokaryotic and human DNA polymerases at the GAA sites.

Conclusions:

• MCND is a novel ligand that specifically binds to d(GAA)(n) repeats.
• The interaction leads to a stable DNA hairpin structure and effectively inhibits DNA polymerase activity.
• MCND shows potential as a tool for studying DNA structure-protein interactions and as a basis for therapeutic development.