Subgenomic RNAs and Their Encoded Proteins Contribute to the Rapid Duplication of SARS-CoV-2 and COVID-19 Progression

Figures

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  Figure 1. Comparison of transcription patterns of positive or negative strand viruses possessing genomes of different lengths. SARS-CoV-2 ((+) strand RNA virus) utilizes RTC (RdRP-formed complex) and TRS for discontinuous transcription to generate (−) strand subgenomic RNAs, which are used as translation templates for the synthesis of (+) strand subgenomic mRNAs. Picornaviruses with smaller genomes, such as enterovirus EV71, directly translate genomic RNA into multimeric proteins, which are cleaved into structural and nonstructural proteins. Influenza virus ((−) strand RNA virus) use itself as a template to synthesize the positive strand, which is transcribed into mRNA. Image created with BioRender (https://biorender.com/ (accessed on 8 August 2022)).

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  Figure 2. Potential mechanism of SARS-CoV-2 variants caused by sgRNAs during replication. (A) The sgRNAs sequence errors occur due to RdRP-mediated base substitution, base deletions, or base insertions. (B) Discontinuous transcription leads to defective sgRNAs formation, including loss of partial viral sequences (gray part) or addition of nonviral sequences (red part). (C) SgRNA replication properties alter because of host-mediated RNA modification or editing. (D) Genetic recombination may occur among different subgenomes to form new subgenomic types. The blue and red parts represent different subgenomic RNA, respectively. Image created with BioRender. (https://biorender.com/ (accessed on 8 August 2022)).

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  Figure 3. SARS-CoV-2 viral proteins and immune responses. SARS-CoV-2 genomic RNA encodes nonstructural proteins, and subgenomic RNA encodes structural and accessory proteins. Among them, subgenomic encoded proteins are involved in multiple steps of inhibiting the production and secretion of IFN-γ and antigen presentation, antagonizing the host innate and acquired immune responses. Image created with BioRender (https://biorender.com/ (accessed on 8 August 2022)).