Off-target messenger RNAs (siRNA-mediated) (siRNA off-targets)

Off-target messenger RNAs (mRNAs) refer to unintended genetic transcripts that are silenced or degraded by small interfering RNAs (siRNAs) due to partial sequence complementarity. This phenomenon typically occurs when the seed region of the siRNA guide strand, spanning nucleotides 2 through 8, matches sequences in the 3' untranslated region (UTR) of non-target mRNAs [1, 2]. This interaction mimics the natural regulatory mechanism of microRNAs (miRNAs), leading to unintended translational repression or mRNA decay [1, 3]. Such interactions can result in the downregulation of hundreds of genes, potentially causing cellular toxicity or confounding therapeutic outcomes [3, 4]. In the context of drug development, these off-target effects represent a significant safety concern, as they can trigger adverse reactions or unintended phenotypic changes in patients [4, 5]. To mitigate these risks, researchers employ chemical modifications, such as 2'-O-methyl substitutions at the second nucleotide of the guide strand, and utilize rigorous bioinformatic screening to ensure high specificity for the intended therapeutic target [5, 6]. Monitoring these off-target interactions is a critical component of the safety assessment for RNAi-based therapeutics like Patisiran and Givosiran [4, 6]. Sources: [1] Jackson, A. L., et al. (2003) Nature Biotechnology; [2] Birmingham, A., et al. (2006) Nature Methods; [3] Fedorov, Y., et al. (2006) RNA; [4] Janas, M. M., et al. (2018) Nature Communications; [5] Jackson, A. L., et al. (2006) RNA; [6] Alnylam Pharmaceuticals (2023) RNAi Therapeutic Platform and Safety.

Other names

miRNA-like off-targetsSeed-mediated off-targetsUnintended mRNA transcriptsNon-specific RNAi targetssiRNA-mediated off-target effects

The siRNA guide strand binds to unintended mRNAs via partial complementarity, primarily through the seed region (nucleotides 2-8), leading to miRNA-like translational inhibition or mRNA decay.