Figure 5. Effect of increasing RIG-I expression on RNA-induced IFNβ activation.

Parallel cultures of RIG-I^−/− MEFs were transfected with pIFNβ-(ff)luciferase and pTK-(ren)luciferase. Some of the cultures were transfected with increasing amounts of plasmids expressing RIG-I. 24 h later, the cultures were transfected in duplicate (or not (none)) with either 3 ug _ppp(ss)RNA1 or 5 ug of poly-I/C. Cell extracts were prepared after a further 20 h, and their luciferase activities were determined. Equal amounts of cell extracts (total protein) were Western blotted with anti-RIG-I. Cross-reacting host bands (h) serve as an internal loading control. The intensities of the RIG-I bands were determined by densitometry and their relative values (RIG-I levels) are plotted above. The insert above shows a blow-up of the IFNβ activation in the absence of any RIG-I.