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Understanding the biological limits of hybridization-dependent siRNA off-target interactions

Luca Penso-Dolfin1, Judith Hauptmann1, Nina Was1

  • 1Silence Therapeutics GmbH, Robert-Rössle-Str. 10, 13125 Berlin, Germany.

Molecular Therapy. Nucleic Acids
|June 29, 2026
PubMed

Insights

Predicting siRNA off-target effects is challenging. This study reveals patterns in low-homology interactions and sequence-dependence in cleavage-independent downregulation, improving in-silico prediction models for RNA interference.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Genetics

Background:

  • Accurate prediction of small interfering RNA (siRNA) off-target effects is crucial for therapeutic applications.
  • Current in-silico methods struggle to fully capture hybridization-dependent off-target interactions, including low-homology and seed-mediated effects.
  • Understanding the mechanisms underlying these off-target events is essential for refining siRNA design.

Purpose of the Study:

  • To investigate the biological limits of low-homology and seed-mediated off-target interactions in siRNA design.
  • To characterize the off-target profiles of promiscuous siRNAs at both mRNA and protein levels.
  • To differentiate between cleavage-dependent and -independent downregulation mechanisms.

Main Methods:

  • Used a cell system with catalytically inactive Argonaute 2 (Ago2) to dissect siRNA-mediated downregulation mechanisms.
  • Measured off-target profiles of six engineered "promiscuous" siRNAs.
  • Analyzed in-silico alignments between siRNA sequences and observed off-target interactions.

Main Results:

  • Observed frequent G:U wobbles and target bulges in off-target interactions, more so than bulges in the siRNA guide strand.
  • Identified a sequence-dependent pattern in cleavage-independent off-target downregulation.
  • Inferred potential issues with siRNA unwinding and loading into the RNA-induced silencing complex (RISC) for modified siRNAs.

Conclusions:

  • The study provides new insights into the mechanisms of siRNA off-target effects, particularly concerning G:U wobbles and bulges.
  • Findings suggest sequence-specific factors influence cleavage-independent downregulation, potentially involving other Argonaute proteins.
  • This research can enhance the accuracy of in-silico prediction tools for siRNA off-target interactions, improving siRNA-based therapeutic design.
Keywords:
MT: Oligonucleotides: therapies and applicationscatalytically inactive Ago2hybridization-dependent siRNA off-targetsmiRNA target alignmentseed-mediated interactionssiRNA cleavagesiRNA designsiRNA off-target alignmentsiRNA off-target prediction

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