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Role of interferon stimulated genes in regulation of the innate antiviral response during vesicular stomatitis virus infection
Viruses are engaged in a constant battle with their hosts for survival. The host employs a range of antiviral defense mechanisms to counter the virus infection, among which, the interferons (IFNs) constitute the first line of antiviral molecules. However, the production of IFNs need to be tightly regulated, since their excess or persistent synthesis may lead to host cell damage, as often seen in many autoimmune diseases. In the work presented here, we have discovered that the IFN-stimulated protein 35 (IFI35 or IFP35) negatively regulates the IFN response during VSV infection. We found that IFI35 is required for VSV replication and that by negatively regulating the RIG-I-mediated antiviral signaling, it facilitates the virus growth. Mechanistically, we demonstrated that IFI35 interacts with RIG-I and promotes K48-linked ubiquitination and degradation through the proteasomal machinery. Further, using an immunoprecipitation coupled with mass spectrometry approach, we identified the E3 ubiquitin ligase Trim21 as an interacting partner of IFI35 as well as another IFN-stimulated protein, Nmi (N-myc interacting protein). We demonstrated that the interaction led to Trim21-mediated K63-linked ubiquitination of Nmi on lysine 22 residue. Importantly, the K63-linked ubiquitination of Nmi appeared to facilitate interaction between Nmi and IFI35 and thereby promoted the negative regulatory function of the Nmi-IFI35 complex. Additionally, we examined the role of phosphorylation in regulating IFI35 function and demonstrated that mutation of a potential phosphorylation site (S287) of IFI35 led to proteasomal degradation of the protein, which could be rescued using the proteasomal inhibitor, MG132. The relevance of this phosphorylation event in regulating IFI35 function is unknown at this time. Overall, these studies have unraveled an intricate interplay of IFI35, Nmi and Trim21 that negatively regulates the innate antiviral response, the failure of which may have implications in the development of various autoimmune diseases.
Das, Anshuman, "Role of interferon stimulated genes in regulation of the innate antiviral response during vesicular stomatitis virus infection" (2015). ETD collection for University of Nebraska - Lincoln. AAI3714910.