Figure 1.

Effects of vincristine and paclitaxel on MAPK activation. (A) Vincristine and paclitaxel induced JNK activation in a time- and dose-dependent manner. MCF-7 cells were treated with vincristine or paclitaxel for various times. The cell lysates were prepared and immunoprecipitated with 10 μg of polyclonal anti-JNK1 antibody followed by 20 μl of protein A Sepharose. The kinase reaction was performed by the procedures described in Materials and Methods. (Upper) The time course of kinase reaction. Represented is the autoradiograph of [γ-³²P]ATP incorporation into exogenous GST-c-Jun-(1–135). (Lower) The dose response of JNK activation. Anti-JNK1 immunocomplexes were obtained with lysates of cells treated with various doses of vincristine or paclitaxel for 30 min. (B) Paclitaxel-induced ERK activity. Cells were treated with paclitaxel (0.1 μM) for various time points, and Western blots were performed by using antibody specific for phosphorylated ERK (Upper) and anti-ERK2 antibody (Lower). (C) Paclitaxel had no effect on p38 activity. Cells were treated with paclitaxel (0.1 μM) for various time points, and Western blots were performed by using antibody specific for phosphorylated p38 (Upper) and anti-p38 antibody (Lower). For a positive control, cells were treated with short-wavelength UV light.