Exposure to KCl alters FMR1 IRES activity and FMRP expression. (A) Dicistronic luciferase mRNA containing the β-globin or FMR1 5' leader inserted into the intercistronic region was transfected into C6 cells and exposed to 50 mM KCl for 30 or 150 min. 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.