RNA interference (RNAi) is a post-transcriptional gene silencing phenomenon mediated by small double-stranded RNA with a length of 20-30nt. This life process is highly conserved during evolution and regulates the transcription and translation of many genes encoding functional proteins.
siRNA (Small interfering RNA) and miRNA (microRNA), as non-coding RNA, are common RNAi tools used in gene function research and disease treatment. siRNA is the simplest and most efficient way to knock down gene expression to study protein function in a wide range of cell types. It is also the best method for clinical treatment and drug development.
miRNA plays an important role as an endogenous gene regulator by mediating translation repression or promoting degradation of target mRNA. While the normal expression and function of miRNA is vital for physiological processes, aberrant expression of miRNAs has been proved to be closely related to the occurrence of various cancers. Perturbation of endogenous miRNA helps to study the function of specific miRNA and maintain therapeutic potential.
RNAi is activated by double-stranded RNA transported into the cytoplasm, and is represented by gene silencing induced by siRNA or shRNA that degrades the target mRNA or induces inhibition of specific mRNA translation. After exogenous dsRNA enters cells, it is first degraded into 21-25nt siRNA under the action of the Dicer enzyme. Subsequently, the antisense strand in the siRNA participates in the synthesis of the guide RNA-induced silencing complex (RISC), which then mediates cleavage of the region complementary to the siRNA antisense strand in the target mRNA molecule, thereby interfering with the function of target gene expression.
Figure 2. Differences between siRNA and miRNA
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Reference  Xu JZ, Zhang JL, et al. Antisense RNA: the new favorite in genetic research. J Zhejiang Univ Sci B. 2018 Oct.;19(10):739-749. Jain, Ritesh G., et al. RNAi-based functional genomics in Hemiptera. Insects 11.9 (2020): 557.
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