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. 2022 Jul 23;13(7):644. doi: 10.1038/s41419-022-05075-2

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© The Author(s) 2022

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

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Fig. 2 — A Antisense oligonucleotides (ASOs) can modulate the target gene expression through two mechanisms. (①) In the occupancy-mediated degradation way, ASOs trigger the target mRNA cleavage by RNase H1 or ribozymes. The Occupancy-only mechanisms do not directly degrade target RNA. Instead, it regulates the gene expression in several ways: (②) alter RNA splicing using splice-switching ASOs to induce exon skipping or exon inclusion; (③) lead to nonsense-mediated mRNA decay (NMD); (④) inhibit or activate translation; (⑤) block the microRNAs binding to target mRNA. B RNA interference (RNAi). Long double-stranded RNA (dsRNA) and precursor microRNA (pre-miRNA) are processed by Dicer into short interfering RNA (siRNA). The antisense strand (indicated as a blue strand) of siRNA is loaded into the RNA-induced silencing complex (RISC) for RNA targeting, degradation or translation repression. C CRISPR/Cas-based RNA editing system includes two Cas nuclease categories, Cas9 and Cas13. A guide RNA(gRNA) binds to Cas9 to cleave ssRNA with (①) or without (②) the help of a protospacer-adjacent motif (PAM). (③) A single CRISPR RNA (crRNA) guides Cas13 to target specific RNA having a protospacer flanking sequence (PFS). (④) In addition to knockdown target RNA, a catalytically deactivated Cas13b (dCas9b) facilitates the A-to-I editing with ADAR. D RNA aptamers function as agonizts or delivery agents. (①) As an antagonist aptamer, Pegaptanib interacts explicitly with vascular endothelial growth factor (VEGF) to inhibit the interaction of VEGF with its receptors, thus treating macular degeneration. (②) Cell type-specific RNA aptamers deliver agents (miRNA, siRNA, shRNA, antibody and chemotherapy drugs) by linking to or conjugating. E mRNA vaccine. (①) The mRNA vaccine against SARS-CoV-2 (mRNA-1273) is delivered into antigen-presenting cells by lipid nanoparticle (LNP). (②)The mRNA encoding SARS-CoV-2 spike protein is released into the cytoplasm and translated to antigen protein by the ribosome. (③) Some antigen proteins are degraded into small peptides by the proteasome and presented to the surface of CD8+ T cells by major histocompatibility complex I (MHCI). The CD8+ cytotoxic T-cell-mediated immunity kills infected cells by secreting perforin or granzyme. (④) Other antigen proteins are degraded in the lysosome and displayed on the surface of T helper cells by MHC II. The B-cell/antibody-mediated humoral immunity uses antibodies to neutralize pathogens.