Consequently,

P and V proteins share the same 317 residues at the amino terminus (P/V common region), while the two proteins have unique carboxyl termini. The V protein contains a 67-residue unique Selleck PD0325901 carboxyl terminus (Vu region), which is characterized by highly conserved 15 amino acids in almost all of the members of the subfamily Paramyxovirinae. The conserved residues include seven cysteine residues, forming a zinc-finger motif that binds two zinc ions (4, 5, 6). Phenotypes of  V-deficient viruses provided insights into the role of the V protein in virus infection in mice (reviewed in (7, 8)). V-knockout virus obtained by mutations at the RNA editing site (SeV V[-]) was cleared from mouse lungs at an early stage of infection, although the virus propagated as efficiently as the wild-type virus in cultured cells (9). A similar phenotype was also observed in SeV possessing truncated V protein lacking the Vu region (SeV VΔC) (10). Both the V(-) and VΔC viruses are remarkably attenuated in virulence in mice, indicating a substantial role of the V protein, predominantly the Vu domain, in SeV pathogenicity in vivo. Amino acid substitutions at the conserved residues of the Vu region also resulted

in suppression of virus growth in mouse lungs and attenuation in virulence, see more accompanying a defect of zinc binding to the mutant Vu region (11, 12). We have shown that growth of SeV V(-) was restored in interferon regulatory factor-3 (IRF3) knockout (KO) mice (13). IRF3 is a transcriptional factor that facilitates expression of IFN and IFN-related genes and plays an important role in innate immunity responding to viral infection. Recent progress in research of innate immunity has revealed detailed signaling pathways leading to IRF3-activation and IFN-β production in response to virus infection (reviewed in (14, 15)). Intracellular dsRNA and/or 5’-terminal triphosphate of RNA generated during viral replication are detected by the cytoplasmic proteins RIG-I (16, 17, 18) and MDA5 (19, 20). TBK-1 and IKKɛ kinases, both of which

Decitabine form a heterotrimeric complex with TANK, are then activated through IPS-1, and IRF3 is further phosphorylated and activated by the activated kinases. Paramyxovirus V proteins including the SeV V protein have been shown to bind MDA5 and to disturb activation of IRF3 and production of β-interferon (19, 20). Thus, it has been hypothesized that V function related to viral pathogenesis can be explained by interaction of V and MDA5. In the present study, we tested this hypothesis by investigating interactions of the mutant V proteins with MDA5. 293T cells (human renal epithelial cells expressing the SV40 large T antigen; Riken Bio Resource Center, Japan) were propagated in DMEM supplemented with 10% fetal calf serum. Wild-type SeV derived from a cDNA of the Z strain (21) and its V mutant viruses were propagated in embryonated chicken eggs.