ABSTRACT
In mammals, early resistance to viruses relies on interferons, which protect differentiated cells but not stem cells from viral replication. Many other organisms rely instead on RNA interference (RNAi) mediated by a specialized Dicer protein that cleaves viral double-stranded RNA. Whether RNAi also contributes to mammalian antiviral immunity remains controversial. We identified an isoform of Dicer, named antiviral Dicer (aviD), that protects tissue stem cells from RNA viruses-including Zika virus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-by dicing viral double-stranded RNA to orchestrate antiviral RNAi. Our work sheds light on the molecular regulation of antiviral RNAi in mammalian innate immunity, in which different cell-intrinsic antiviral pathways can be tailored to the differentiation status of cells.
Subject(s)
DEAD-box RNA Helicases/genetics , DEAD-box RNA Helicases/metabolism , RNA Interference , RNA Viruses/physiology , RNA, Viral/metabolism , Ribonuclease III/genetics , Ribonuclease III/metabolism , Stem Cells/enzymology , Stem Cells/virology , Alternative Splicing , Animals , Brain/enzymology , Brain/virology , Cell Line , DEAD-box RNA Helicases/chemistry , Humans , Immunity, Innate , Isoenzymes/chemistry , Isoenzymes/genetics , Isoenzymes/metabolism , Mice , Organoids/enzymology , Organoids/virology , RNA Virus Infections/enzymology , RNA Virus Infections/immunology , RNA Virus Infections/virology , RNA Viruses/genetics , RNA Viruses/immunology , RNA, Double-Stranded/metabolism , RNA, Small Interfering/metabolism , Ribonuclease III/chemistry , SARS-CoV-2/genetics , SARS-CoV-2/immunology , SARS-CoV-2/physiology , Virus Replication , Zika Virus/genetics , Zika Virus/immunology , Zika Virus/physiology , Zika Virus Infection/enzymology , Zika Virus Infection/immunology , Zika Virus Infection/virologyABSTRACT
Being opportunistic intracellular pathogens, viruses are dependent on the host for their replication. They hijack host cellular machinery for their replication and survival by targeting crucial cellular physiological pathways, including transcription, translation, immune pathways, and apoptosis. Immediately after translation, the host and viral proteins undergo a process called post-translational modification (PTM). PTMs of proteins involves the attachment of small proteins, carbohydrates/lipids, or chemical groups to the proteins and are crucial for the proteins' functioning. During viral infection, host proteins utilize PTMs to control the virus replication, using strategies like activating immune response pathways, inhibiting viral protein synthesis, and ultimately eliminating the virus from the host. PTM of viral proteins increases solubility, enhances antigenicity and virulence properties. However, RNA viruses are devoid of enzymes capable of introducing PTMs to their proteins. Hence, they utilize the host PTM machinery to promote their survival. Proteins from viruses belonging to the family: Togaviridae, Flaviviridae, Retroviridae, and Coronaviridae such as chikungunya, dengue, zika, HIV, and coronavirus are a few that are well-known to be modified. This review discusses various host and virus-mediated PTMs that play a role in the outcome during the infection.