Fig. 2.
Dimerization/oligomerization of DAI activates immune response. (a) Dimer/oligomer formation of DAI by B-DNA stimulation. HA-tagged DAI (HA-DAI) and FLAG-tagged DAI (FLAG-DAI) were transiently coexpressed in L929 cells. The cells were stimulated with 6 μg/ml B-DNA for the indicated periods and analyzed by immunoprecipitation with anti-FLAG antibody, followed by immunoblotting with anti-HA (Upper) and anti-FLAG (Lower) antibodies. (b) Dimerization of DAI induces type I IFN production. HA-DAI or Fv (Fv-vector) or Fv-fused DAI (Fv-DAI) was transiently expressed in L929 cells. The cells were treated with AP20187 for the indicated periods, and the expressions of IFN-β (Top), IFN-α4 (Middle), and GAPDH (Bottom) mRNAs were assessed by RT-PCR. Results from B-DNA treatment on L929 cells are also shown. (c) DAI-WT, DAI-A1, or DAI-A2 was transiently expressed in L929 cells with either FLAG-TBK1 (Upper) or FLAG-IRF3 (Lower). These cells were stimulated with B-DNA and analyzed by immunoprecipitation with anti-FLAG antibody, followed by immunoblotting with anti-HA and anti-FLAG antibodies. The relative band intensities depicted in the graphs are of B-DNA-treated samples measured by a densitometer normalized to those of unstimulated sample.