Single-Stranded Silencing RNAs: Hit Rate and Chemical Modification

Area of Science:

• Molecular Biology
• Oligonucleotide Chemistry
• Gene Silencing

Background:

• Single-stranded silencing RNAs (ss-siRNAs) leverage RNA interference machinery for gene silencing.
• ss-siRNAs aim to combine advantages of antisense oligonucleotides and siRNAs.
• Previous research focused on phosphate and oligonucleotide body modifications.

Purpose of the Study:

• To develop and optimize ss-siRNAs based on active siRNA duplexes.
• To investigate the impact of 3 -terminal dinucleotide chemistry on ss-siRNA potency.
• To compare the efficacy of 2 -O-Me-RNA and 2 -O-methoxyethyl-RNA (MOE) modifications.

Main Methods:

• Design and synthesis of ss-siRNAs based on five active siRNA sequences.
• Evaluation of ss-siRNA activity and toxicity.
• Assessment of 3 -terminal dinucleotide modifications, including 2 -O-Me-RNA, MOE, and locked nucleic acid (LNA).

Main Results:

• Three of five tested sequences showed no ss-siRNA activity; two exhibited increased toxicity.
• Two sequences demonstrated effective ss-siRNA activity.
• Oligomers with 2 -O-Me-RNA 3 -terminal modifications showed significantly improved potency and activity compared to MOE analogs.
• LNA modifications improved activity for one sequence over MOE.

Conclusions:

• The 3 -terminal dinucleotide chemistry is critical for ss-siRNA potency.
• 2 -O-Me-RNA modifications enhance ss-siRNA performance and accessibility due to lower cost.
• Optimized ss-siRNAs present a promising tool for gene silencing applications.