ERKs are involved in the transcriptional regulation of IEX-1. UT7-Mpl cells were transiently transfected with 400 ng pLucIEXp (A) or with 400 ng pGL2-3 × AML1 and AML1 expression plasmid, as indicated (B). Cells were stimulated with 10 nM TPO in the presence or absence of 10 μM U0126 and harvested 20 hours later for luciferase assays. The results shown represent the mean ± SD of at least 3 separate experiments. *P < .05.