Ru-indoloquinoline complex as a selective and effective human telomeric G-quadruplex binder

Area of Science:

• Medicinal Chemistry
• Biochemistry
• Molecular Biology

Background:

• Indoloquinoline derivatives are known G-quadruplex binders that can inhibit telomerase.
• The interaction of metal complexes with indoloquinoline moieties, particularly with G-quadruplex DNA, is less understood.
• G-quadruplex structures are crucial in telomere maintenance and oncogene regulation.

Purpose of the Study:

• To investigate the binding interaction of a novel ruthenium complex, [Ru(bpy)2(itatp)]2+, containing an indoloquinoline moiety with human telomeric (Telo22) and c-myc (Pu27) G-quadruplex DNA.
• To determine the selectivity of the ruthenium complex towards different G-quadruplex structures.
• To elucidate the conformational changes induced by the ruthenium complex in G-quadruplex DNA.

Main Methods:

• UV-visible (UV-Vis) spectroscopy
• Fluorescence spectroscopy
• Fluorescent Intercalator Displacement (FID) assay
• Thermal denaturation studies
• Circular Dichroism (CD) spectroscopy

Main Results:

• The ruthenium complex [Ru(bpy)2(itatp)]2+ exhibits strong π-π stacking interactions and a high binding constant (∼10(7) M(-1)) with human telomeric G-quadruplex (Telo22).
• The complex shows moderate binding affinity towards c-myc G-quadruplex (Pu27), indicating significant selectivity for the telomeric G-quadruplex.
• CD spectroscopy revealed that the complex converts Telo22 into an antiparallel G-quadruplex conformation and disrupts the parallel G-quadruplex structure of Pu27.

Conclusions:

• The ruthenium complex [Ru(bpy)2(itatp)]2+ is a selective binder of human telomeric G-quadruplex DNA.
• The complex stabilizes antiparallel G-quadruplex conformations and destabilizes parallel G-quadruplex structures.
• This selectivity and conformational modulation suggest potential applications in targeting G-quadruplexes for therapeutic purposes.