Quadruplex structure of Oxytricha telomeric DNA oligonucleotides

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• Eukaryotic telomeres feature G-rich sequences with 3' single-strand overhangs.
• G-rich oligonucleotides may form four-stranded structures in vivo.
• Hoogsteen base-paired G-quartets are proposed structural motifs.

Purpose of the Study:

• To investigate the conformations of specific DNA oligonucleotides containing the Oxytricha telomere repeat.
• To elucidate the structural basis of proposed four-stranded telomeric DNA structures.

Main Methods:

• 1H NMR spectroscopy was employed to study DNA oligonucleotide structures.
• Conformational analysis of d(G4T4G4) (Oxy-1.5) and d(G4T4G4T4G4T4G4) (Oxy-3.5) was performed.

Main Results:

• Oxy-1.5 folded into a symmetrical bimolecular quadruplex.
• Oxy-3.5 formed an intramolecular quadruplex.
• Both structures contained four G-quartets with alternately syn and anti nucleotides, differing from prior models.
• T4 loops in Oxy-1.5 exhibited diagonal looping and alternating parallel/antiparallel strand arrangements.

Conclusions:

• The study reveals specific quadruplex structures formed by Oxytricha telomere repeats.
• The observed nucleotide and loop arrangements provide new insights into four-stranded DNA conformations.
• Findings contribute to understanding the structural relevance of G-rich overhangs in telomeres.