FIG. 3.

Progestin-induced sustained Erk1/2 MAPK signaling requires transcription and translation. (A) T47D-YB cells were treated for 20 h with or without R5020 in the presence of H₂O vehicle control, CHX, EtOH vehicle control, or DRB, and phospho- (p) and total (t) Erk1/2 MAPKs were detected by Western blotting of whole-cell lysates. (B) T47D-YB cells were pretreated for 30 min with DMSO vehicle control or U0126 (MEK inhibitor) prior to addition of R5020. After 30 to 60 min, U0126 was washed out of the cultures represented in lanes 5 and 6 (U0 w/o; the 45-min time is shown). Cell lysates were collected after 18 h and Western blotted for phospho- or total Erk1/2 MAPKs and PR. The experiments were repeated three times with similar results.