Small molecule inhibition of RISC loading

Area of Science:

• Molecular Biology
• Biochemistry

Background:

• Argonaute proteins (Ago) are central to RNA silencing pathways, regulating microRNA and siRNA function.
• Ago2, a key Argonaute protein, possesses RNA binding and nuclease activities essential for these processes.
• Existing methods lack efficiency for large-scale screening of modulators for microRNP/RISC loading.

Purpose of the Study:

• To develop and validate a novel in vitro fluorescence polarization assay for screening microRNP/RISC loading modulators.
• To identify small molecules that inhibit the loading of small RNAs into Ago2.

Main Methods:

• A fluorescence polarization assay utilizing TAMRA-labeled RNAs and human Ago2 was established.
• The assay was employed for high-throughput screening of small-molecule inhibitors.
• Inhibitor efficacy was confirmed by assessing siRNA loading into endogenous Ago2 in cultured cells.

Main Results:

• The novel assay successfully identified potent small-molecule inhibitors of RISC loading.
• Aurintricarboxylic acid (IC50 = 0.47 μM), suramin (IC50 = 0.69 μM), and oxidopamine HCl (IC50 = 1.61 μM) were identified as effective inhibitors.
• These compounds demonstrated inhibitory activity against siRNA loading into endogenous Ago2 in cell-based assays.

Conclusions:

• A robust and scalable in vitro assay for screening RISC loading modulators has been developed.
• The identified small molecules represent valuable tools for studying RNA silencing mechanisms.
• This assay facilitates the discovery of novel therapeutics targeting RNA-mediated gene regulation.