Journal: Journal of Virology
Article Title: Replication of Human Norovirus RNA in Mammalian Cells Reveals Lack of Interferon Response
doi: 10.1128/JVI.01425-16
Figure Lengend Snippet: Replication of plasmid-derived U201 RNA does not induce an IFN response. (A) Schematic drawing of U201 genome transcript RNAs expressed from plasmids. Note that the Δ4607 mutation causes a frameshift and premature termination of Pol, creating an untranslated region between ORF1 and ORF2. (B) Western blotting of U201 polymerase (Pol), p35 (Nterm), and p41 in 293FT cells transfected with U201 or U201-Δ4607 plasmid for 24 h. A nonspecific protein band served as an equal loading control. (C) Laser scanning confocal microscopy images of 293FT cells transfected with U201 or U201-Δ4607 plasmid for 24 h. Cells were labeled with mouse monoclonal antibody to U201 VPg (red) and guinea pig antibody to U201 VP1 (green). Nuclei were counterstained with DAPI (blue). Scale bars, 10 μm. The merged images show that both plasmids express ORF1 polyproteins (VPg-positive), but RNA replication (VP1-positive) occurs in only one of the U201-transfected cells, not in U201-Δ4607-transfected cells. (D) IFN-β-Luc reporter assay. 293FT cells were transfected with IFN-β-Luc reporter in combination with vector, U201, or U201-Δ4607 plasmid for 24 h. As a positive control, vector-transfected cells were infected with SeV (40 HA/ml) for 18 h. Luciferase activity was first normalized to that of an internal RLuc transfection control and then normalized to that of vector-transfected cells and is presented as fold induction. (E and F) RLuc and IFN-β-Luc dual reporter assay. 293FT cells were transfected with IFN-β-Luc reporter in combination with vector, U201-RLuc, or U201-Δ4607-RLuc plasmid for 24 h. As a positive control, vector-transfected cells were infected with SeV (40 HA/ml) for 18 h. RLuc activity is presented as original relative light units/second (RLU/s). Luciferase activity was normalized to that of vector-transfected cells and is presented as fold induction. (G) Western blotting of ISG56 in the same cell lysates as used in the experiments shown in panels E and F. Actin served as an equal loading control.
Article Snippet: The 293FT cell line, derived from human embryonic kidney HEK293 cells transformed with the simian virus 40 (SV40) large T antigen, was purchased from Invitrogen.
Techniques: Plasmid Preparation, Derivative Assay, Mutagenesis, Western Blot, Transfection, Confocal Microscopy, Labeling, Reporter Assay, Positive Control, Infection, Luciferase, Activity Assay