Supplementary Figure 5: ELF4 is a new type I interferon regulatory factor.

(a) ELF4 siRNA, MAVS siRNA or scrambled siRNA were transfected into 293T cells. The cells were infected with SeV 36 hours after transfection, with medium (Med) as a control. 16 hours later, the dimerization of IRF3 was detected by native PAGE and immunoblotting. The knockdown efficiency was analyzed by SDS PAGE and immunoblotting. Data were pooled from 3 independent experiments. (b) 293 cells were co-transfected with HA tagged ELF4 and MAVS or TBK1 with or without VSV tagged STING. Cell lysates were immunoprecipitated with Flag and blotted with HA or Flag antibodies. Whole cell lysates (WCL) were blotted with Flag or HA antibodies. Data were pooled from 3 independent experiments. (c) HEK293T cells were treated with medium or SeV. 6 hours later, cell lysates were immunoprecipiated (IP) by anti-ELF4, and immunoblotted (IB) by indicated antibody. Data were pooled from 3 independent experiments. (d) Wild-type or the indicated mutants of ELF4 and IFNβ-Luc were transfected into 293T cells. **P<0.01 as determined by Student's t-test. Data were pooled from 3 independent experiments. There are 2 technical replicates within each experiment. (e) In vitro expressed ELF4 and mutantELF4 was incubated with TBK1. The kinase activity of TBK1 is detected by luciferase assay. **P<0.01 as determined by Student's t-test. Data were pooled from 3 independent experiments. There are 2 technical replicates within each experiment. (f&g) Wild type and Elf4^-/- pDCs were treated with CpG DNA. 8 hours later, the supernatants were transfer to L929-ISRE-Luc cells, followed by luciferase assay (f). The cellular Cxcl10 transcript abundance was quantified by qRT-PCR (g). Data were pooled from 3 independent experiments. There are 2 technical replicates within each experiment. (h&i) Wild-type or the indicated mutants of ELF4 were transfected into 293T cells. Native PAGE and Co-immunoprecipitation were performed at 24 hour after transfection. Data were pooled from 3 independent experiments. (j) Immune fluorescence image of 293T cells to analyze the location of exogenous HA-ELF4 at the indicated time after transfection. Data were pooled from 3 independent experiments. (k) WT or TBK1^-/- MEF cells were infected with SeV and the location of ELF4 was determined by microscopy. Data were pooled from 3 independent experiments. (l) HEK293T were transected with wild-type or the indicated mutants and the location of ELF4 was determined by microscopy. Data were pooled from 3 independent experiments. (m) Wild-type or the indicated mutants of ELF4 and IFNβ-Luc were transfected into 293T cells. ****P<0.0001 as determined by Student's t-test. Data were pooled from 3 independent experiments. There are 2 technical replicates within each experiment. (n) There are three GGAA and one ETS-IRF composite element (EICE) in IFNβ promoter. There are four GGAA and one EICE in IFNα2 promoter. There are one GGAA and one EICE in IFNα4 promoter.