3C). Collectively, these data clearly demonstrate that Mal modulates IFN-β gene induction whereby the TIR domain of Mal inhibits the PRDI-III reporter gene. Given that TRIF is essential for poly(I:C)-mediated signalling via TLR3 17, we tested the ability of Mal to modulate TRIF-dependent gene induction. Correlating with the previous reports 25, ectopic expression of TRIF potently activated the IFN-β reporter gene (Fig. 4A). We found that although ectopic expression of Mal or the TIR domain of Mal dose-dependently inhibited TRIF-induced activation of the IFN-β reporter gene, the N-terminal

Compound Library datasheet region of Mal did not inhibit, but rather, augmented IFN-β reporter gene activity (Fig. 4A). Further, we found that Mal-TIR inhibited the induction of the IFN-β reporter gene by Mal-N-terminal. As a control, we found that the TLR adaptor TRAM did not inhibit TRIF-induced activation of the IFN-β reporter gene (Fig. 4A). To preclude the possibility that Mal may exert its effects through poly(I:C)-mediated activation of the RLR, retinoic acid-inducible gene I (RIG-I) or melanoma differentiation-associated antigen 5 (Mda-5), rather than through TLR3/TRIF, cells were co-transfected with a plasmid encoding either RIG-I or Mda-5 and increasing amounts of Mal. Although ectopic expression of

RIG-I and Mda-5 activated the IFN-β reporter gene, Mal did not inhibit, but rather augmented RIG-I/Mda-5-mediated IFN-β reporter gene activity (Fig. 4E). As expected, although TRIF activated the NF-κB and the PRDIV reporter Selleck BGB324 genes (Fig. 4B and C), Mal and its variants did not inhibit TRIF-induced activation of the NF-κB (Fig. 4B) and PRDIV reporter genes (Fig.

4C). Also, although Mal and the TIR domain of Mal inhibited TRIF-induced activation of the PRDI-III reporter gene (Fig. 4D), the N-terminal region of Mal did not (Fig. 4D). Taken together, these data clearly demonstrate that Mal modulates TRIF-mediated IFN-β gene induction whereby the TIR domain of Mal inhibits the TRIF-induced activation of the PRDI-III reporter gene. Moreover, Cepharanthine the inhibitory role of Mal in poly(I:C)-mediated induction of IFN-β is TLR3/TRIF dependent and involves the PRDI-III enhancer element of the IFN-β promoter. Given that the data presented thus far provide compelling evidence that Mal negatively regulates IFN-β induction by blocking the PRDI-III element, we sought to establish whether this effect was mediated through IRF3 or IRF7. To this end, we transfected HEK293 cells with either the IFN-β or the PRDI-III luciferase reporter constructs and plasmids encoding either IRF3 or IRF7. Given that both IRF are weak activators of the IFN-β promoter 27, we opted to co-transfect the cells with TRIF (10 ng) to enhance the signal output and to aid in the engagement of auxiliary molecules necessary for IFN-β and PRDI-III gene induction. In addition, cells were co-transfected with increasing amounts of Mal, Mal-TIR or N-Mal.