FIG. 8.

Regulation of ERK-dependent nuclear events by Mxi2. (A, left side) Effects of Mxi2 on Elk1-dependent gene expression. Elk1transactivation was examined in NIH 3T3 cells cotransfected with GAL4-Elk1 (TAD) and the indicated plasmids. ERKs were HA tagged; p38 and Mxi2s were AU5 tagged (Mx + DK = Mxi2 + ERK2 DK). The results shown are the average ± the standard error of the mean of at least five independent experiments. (Bottom) Expression levels of the different kinases. (Right side) Effects of Mxi2 on Elk1transactivation induced by EGF in 293T cells. The results shown are the average ± the standard error of the mean of three independent experiments. In both parts, values are expressed relative to the activity detected in vector-transfected cells. Luciferase activities were normalized to the β-galactosidase activity. (B) Effect of Mxi2 on Elk1 phosphorylation. 293T cells were transfected with HA-Elk1 with (+) or without (−) AU5-Mxi2 and stimulated with cotransfected MEK1E or with EGF (100 ng/ml) for 20 min, 2 h, and 5 h as shown. Phospho-Elk1 levels were determined by immunoblotting. (Bottom) Expression of HA-Elk1. (C) Effects of Mxi2 on HIF1α-dependent expression. HIF1α transactivation was determined in NIH 3T3 cells cotransfected with GAL4-HIF1α (TAD) and the indicated plasmids. Luciferase activities were normalized to the β-galactosidase activity. Values are expressed relative to the activity detected in vector-transfected cells. The results are the average ± the standard error of the mean of three independent experiments. WB, Western blot; c, control.