Figure 1.
Conditional expression of MKP-1 inhibits UV-induced SAPK and p38 MAPK activity. (A) U937 cells were transfected with either hMTIIa vector or hMTIIa-MKP-1(myc) and stable cell lines derived by selection in the presence of hygromycin B. Cells were metabolically labeled for 4 h with [35S]methionine in the presence or absence of 1 μM CdSO4 (Cd++). MKP-1(myc) protein was immunoprecipitated from whole-cell extracts with the anti-Myc antibody 9E10, resolved by SDS/PAGE, and visualized by fluorography. (B) U937 cells expressing hMTIIa-MKP-1 were pretreated in the absence or presence of 1 μM CdSO4 for 4 h before exposure to UV irradiation (200 J/m2). Cells were incubated for the indicated times and SAPK and p38 MAPK activity determined as described in Materials and Methods.