FIG. 6.

The RARα activation capacity of HCV core was reduced by RNAi elimination of endogenous Sp110b. (A) RNAi elimination of endogenous Sp110b protein in HeLa cells. Extracts from cells treated with 300 U of gamma interferon/ml after transfection with either an siRNA specific for Sp110 and Sp110b [Sp110(b)-siRNA] or a randomized siRNA (control-siRNA) was analyzed with an antibody recognizing both Sp110 and Sp110b (upper panel) or anti-α-tubulin (lower panel). As a positive control, small amounts of extracts from cells overproducing FLAG-tagged Sp110 or Sp110b were also analyzed. Positions of molecular size markers (in kilodaltons) are given on the right. (B) HeLa cells were transfected with control-siRNA (bars 1 and 2) or Sp110(b)-siRNA (bars 3 and 4). At 24 h posttransfection, plasmid transfection with 25 ng of pRARE-Luc and 300 ng of either pKS+/CMV (bars 1 and 3) or pCMV-core (bars 2 and 4) was carried out. An additional 24 h later, the cells were harvested; luciferase activity was measured as described in the legend to Fig. 2A. Data are means of the relative luciferase activities in three independent experiments. Comparisons of luciferase activities (bars 1 versus 2 [×2.69] and bars 3 versus 4 [×1.30]) are shown above the graph. The combinations of siRNAs and plasmids used are indicated below the graph.