Fig. 7. p42/p44 MAPKs constantly shuttle between the nucleus and the cytoplasm and their localization is dependent on the balance between nuclear and cytoplasmic anchors throughout stimulation. (A) Quiescent CCL39 cells (a,b) or 5 minutes 10% serum stimulated CCL39 cells (c,d) were either left untreated (a,c) or treated for 5 minutes with 5 ng/ml of the active nuclear export inhibitor Leptomycine B (LMB) (b,d). (B) Quiescent CCL39 cells were stimulated for 3 hours with 10% serum and either left untreated (a), treated for 10 minutes with 5 ng/ml LMB (b), treated for 10 minutes with 10 µM of the MEK inhibitor UO126 (c), or treated for 10 minutes with both LMB and UO126 (d). Indirect immunofluorescence detection was performed with the polyclonal antibody anti-p42/p44 MAPKs from UBI.