Figure 3.

p53-dependent ERK activation in response to DNA damage. (A Left) Activation of ERK and inhibition by MEK-specific inhibitor PD98059 in 501T cells in response to UV irradiation. Human NDFs (501T) were treated as described in Materials and Methods in the presence or absence PD98059 (20 μM) for 24 h. As a control, cells were treated with the same amounts of DMSO, the solvent for the inhibitor. Cells were harvested for analysis of protein expression, and Western blots were carried out with antibodies against p53, p21, pp-ERK, or total ERK. (A Right) Activation of ERK in 501T cells in response to MMC treatment. 501T cells were treated with 10 μg/ml MMC for 36 h. Lysates were made, and Western blots were performed as described above. (B) Activation of ERK in primary MEFs derived from wt and p53-null mice embryos. Cell lysates were prepared after treatment with DNA-damaging agents [10 μg/ml MMC or 5 ng/ml actinomycin D (Act. D)] for the indicated time periods. Western blots were performed with antibodies against p53, pp-ERK, and total ERK, respectively.