Human telomeric sequence forms a hybrid-type intramolecular G-quadruplex structure with mixed parallel/antiparallel...

Area of Science:

• Biochemistry
• Structural Biology
• Genetics

Background:

• Human telomeric DNA contains repetitive sequences (TTAGGG) that form G-quadruplex structures.
• G-quadruplexes in telomeric DNA can inhibit telomerase activity, making them potential cancer therapeutic targets.
• Understanding the precise structure of telomeric G-quadruplexes under physiological conditions is vital for drug design.

Purpose of the Study:

• To determine the folding structure of human telomeric DNA in a potassium (K+) solution using Nuclear Magnetic Resonance (NMR).
• To elucidate the G-quadruplex topology relevant for structure-based drug design against cancer.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy was employed to analyze the structure of the human telomeric DNA sequence (Tel26) in K+ solution.
• The study focused on determining the G-quadruplex folding topology and its characteristics.

Main Results:

• A novel intramolecular G-quadruplex folding topology with hybrid-type mixed parallel/antiparallel G-strands was identified.
• This structure features three G-tetrads connected by specific loops (TTA), distinct from previously reported structures.
• The hybrid-type G-quadruplex is the predominant conformation for Tel26 in K+ solution and is readily formed upon K+ addition.

Conclusions:

• The identified hybrid-type G-quadruplex structure provides a comprehensive explanation for experimental data on human telomeric G-quadruplexes in K+.
• This finding offers insights into the polymorphism and interconversion of telomeric G-quadruplex structures.
• The unique topology of this G-quadruplex presents a promising target for developing specific small molecule drugs for cancer therapy.