Highly stable DNA triplexes formed with cationic phosphoramidate pyrimidine alpha-oligonucleotides

Area of Science:

• Biochemistry
• Molecular Biology
• Oligonucleotide Chemistry

Background:

• DNA triplex formation is crucial for gene regulation and therapeutic applications.
• Pyrimidine-based alpha-oligonucleotides (alpha-ONs) are investigated for their triplex-forming potential.
• Modifying phosphodiester linkages can influence oligonucleotide stability and binding affinity.

Purpose of the Study:

• To investigate the triplex-forming ability of cationic phosphoramidate pyrimidine alpha-oligonucleotides (alpha-ONs) with DNA duplexes.
• To evaluate the impact of positively charged phosphoramidate linkages on triplex stability and formation kinetics.
• To assess the sequence specificity of triplex recognition mediated by cationic alpha-ONs.

Main Methods:

• UV melting experiments to determine triplex stability.
• Circular dichroism spectroscopy to analyze structural changes.
• Gel mobility shift assays to confirm triplex formation and binding.

Main Results:

• Cationic phosphoramidate alpha-ONs exhibit enhanced triplex formation compared to their phosphodiester counterparts.
• Triplex stability increases with the number of positive charges in the phosphoramidate linkages.
• A fully cationic phosphoramidate alpha-TFO forms a highly stable triplex with fast association kinetics at neutral pH and without magnesium ions.
• Hoogsteen base pairing ensures high sequence specificity in DNA duplex recognition by cationic alpha-TFOs.

Conclusions:

• Cationic phosphoramidate alpha-oligonucleotides represent a promising class of molecules for stable DNA triplex formation.
• These findings present the first report of stable pyrimidine motif triplexes formed by cationic alpha-oligonucleotides and duplex targets.
• The enhanced stability and rapid association kinetics suggest potential applications in molecular biology and therapeutics.