Telomerase protein rather than its RNA is the target of phosphorothioate-modified oligonucleotides

Area of Science:

• Molecular Biology
• Biochemistry
• Cancer Research

Background:

• Human telomerase is a ribonucleoprotein essential for telomere maintenance.
• Telomerase is upregulated in most cancers, making it a promising therapeutic target.
• Oligonucleotides are investigated for their potential to modulate telomerase activity.

Purpose of the Study:

• To evaluate the efficacy of modified oligonucleotides in inhibiting human telomerase activity.
• To elucidate the binding interactions of these oligonucleotides with telomerase.
• To explore novel oligonucleotide designs for cancer therapy.

Main Methods:

• Telomerase activity was assessed using the TRAP-ez assay on HL-60 cell extracts.
• Kinetic studies were performed to determine binding interactions and inhibition constants.
• Various modified oligonucleotides, including phosphorothioate-modified oligonucleotides (PS-ODNs) and peptide nucleic acids, were tested.

Main Results:

• PS-ODNs demonstrated potent inhibition of telomerase activity at subnanomolar concentrations, outperforming peptide nucleic acids.
• PS-ODNs preferentially bind to the primer binding site of telomerase, exhibiting competitive inhibition with the TS primer.
• PS-modification of the TS primer itself led to a significant increase in telomerase activity, dependent on the degree of modification.

Conclusions:

• PS-ODNs are highly effective inhibitors of human telomerase, targeting its primer binding site.
• The unexpected enhancement of telomerase activity by PS-modified TS primers suggests complex regulatory mechanisms.
• Chimeric oligonucleotides, combining PS-modified elements for primer site targeting and RNA-targeting sequences, are proposed for optimized therapeutic design.