| Popis: |
Tick-borne encephalitis virus (TBEV) is a positive-single stranded RNA Virus belonging to the Flaviviridae family. Flaviviruses replicate in the cytoplasm of infected cells and therefore during the different viral steps viral RNA is exposed to diverse cellular responses. The contribution of host RNA-binding proteins to flaviviral replication is an important issue under investigation. T-intracellular antigen-1 (TIA-1) is a stress-induced RNA-binding protein shown to be involved in the repression of initiation of translation of cellular mRNAs. When cells are subjected to UV radiation, heat shock, oxidative stress, as well as to certain viral infections, TIA-1 migrates from the nucleus and accumulates to form cytoplasmic foci named stress granules (SG). In this work I show that TIA-1 and TlAR knockdown by RNAi in human cells led to an increase of TBEV RNA levels as well as extracellular infectivity. Taking advantage of a TBE-luciferase replicon system developed in our lab, I could demonstrate that TIA-1 affected viral replication, more specifically at the level of the initial round of translation. I could also show by RNA immuneprecipitation of TIA-1 that the protein was interacting with viral RNA in TBEV infected cells. Moreover, during TSEY infection, cytoplasmic TIA-l was recruited at perinuclear sites of viral replication with concomitant depletion of TIA-l SOs. This effect was TIA-1 specific since 03BPI, another SO protein, remained in SGs and did not re-localize to sites of viral replication. In addition, heat-shock induction of TIA-1 SGs, but not G3BP1 SGs, was inhibited in TBEV infected cells. I could observe that G3BP SG contained RIG-I protein in TBEV infected cells and also I could demonstrate that RIG-I was involved in the activation of IFNβ expression upon TBEV infection. Moreover, I could show that G3BP SG were forming around the same time in which IFNβ was induced in TBEV infected cells, leading to the hypothesis of a possible cross-talk between stress pathway and immune response during TBEV infection. In conclusion, I could demonstrate that TIA-1 is recruited to sites of viral replication, binds to viral RNA and negatively regulates viral replication, possibly by inhibiting the first round of viral translation. |
