FIGURE 16-26 Induction of gene transcription by MAP kinase. Steps 1–3: In the cytosol, MAP kinase phosphorylates and activates the kinase p90^RSK, which then moves into the nucleus and phosphorylates the SRF transcription factor. Steps 4 and 5: After translocating into the nucleus, MAP kinase directly phosphorylates the transcription factor TCF, which is already bound to the promoter of the c-fos gene. Step 6: Phosphorylated TCF and SRF act together to stimulate transcription of c-fos and other genes that contain an SRE sequence in their promoter. See the text for details. See R. Marais et al., 1993, Cell 73:381, and V. M. Rivera et al., 1993, Mol. Cell Biol. 13:6260.