FIG. 2.
Mutation of the Rb1 pathway inhibits activation of the c-Raf/Mek/Erk pathway, and Ras activation does not overcome this inhibition. (A) Western blot showing the levels of phosphorylated (P) Erk1/2 in proliferating cells. (B) Western blot analysis of the effects of serum starvation followed by readdition of serum on Erk phosphorylation. (C) Western blot showing the levels of phosphorylated c-Raf in proliferating cells. (D) Western blot showing the effects of serum starvation (−) and readdition of serum (+, 30 min after serum addition) on c-Raf phosphorylation. (E) The cells in panel D were assessed for phosphorylation of Mek. Lanes not used in the original blot were spliced out.