MEK/ERK inhibition affects c-Myc phosphorylation and expression in RD cells. A. Cell lysates from RD cells untreated (-) or treated (+) with 10 μM U0126 for indicated times were analysed by immunoblotting with specific antibodies for indicated proteins. α-tubulin expression shows the loading of samples. B. Cells were transfected with control (C) or ERK1, ERK2, ERK1/2 siRNAs and cultured for 3 days. Immunoblot of total lysates were performed using specific antibodies recognizing the indicated proteins. The values of fold increases over the control, arbitrarly set at 1, were obtained by densitometric analysis (A and B lower panels). C. Myc-Max heterodimer in RD cells untreated (-) or treated (+) with U0126 for 12 hours. Myc-Max complex was immunoprecipitated (IP) with a Max monoclonal antibody from extracts containing equal amounts of total proteins and subsequently analysed by immunoblotting with a c-Myc polyclonal antibody. Same filter was probed with a Max polyclonal antibody. Similar results were obtained in two different experiments.