Exposure to poly I:C alters FMR1 IRES activity. (A) Dicistronic luciferase mRNA containing the β-globin or FMR1 5' leader inserted into the intercistronic region were transfected into C6 cells and exposed to 500 μg/ml of poly I:C. After seven hr the cells were assayed for Photinus and Renilla luciferase activity. (B) Lysates from cells treated in (A) were analyzed for FMRP and GAPDH (as a loading control) using Western blots. Shown is a representative Western blot; each experiment was performed in triplicate, n = 3. (C) Protein expression was quantitated using ImageQuant software; FMRP levels were normalized to GAPDH expression.