Figure 5.

Myc inhibits ERK signaling in MEFs. (a) Western blot analysis of pERK and reprogramming factor expression in normal OG-MEFs (passage no. 2) separately infected with retroviruses encoding reprogramming factors or DsRed for 4 days. pMXs, pMXs-retrovirus. (b) Western blot analysis of pERK and reprogramming factor expression in siOG-MEFs separately infected with lentiviruses encoding Dox-inducible reprogramming factors or DsRed after 3 days of Dox treatment. (c) Western blot analysis of pERK and Myc expression in the Dox-inducible Myc expressing siOG-MEFs treated with various concentrations of Dox for 3 days. (d) Western blot analysis of pERK and reprogramming factor expression in the iOSK-expressing siOG-MEF clones separately infected with lentiviruses encoding Dox-inducible Oct4, Sox2 and Klf4. Cells were treated with Dox (4 μg ml⁻¹) for 3 days. (e) Western blot analysis of pERK and Myc expression in the iOSK-expressing clone C-22 infected with a lentivirus encoding Dox-inducible DsRed or Myc for 24 h. Cells were treated with Dox (0.1 μg ml⁻¹) for 3 days. (f) Western blot analysis of pERK and reprogramming factor expression in normal OG-MEFs (passage no. 3) infected with a lentivirus encoding Dox-inducible OKS as a single polycistronic unit. Cells were treated with Dox (4 μg ml⁻¹) for 3 days. Alternatively, after co-infection with a retrovirus encoding DsRed or Myc, cells were treated with Dox (4 μg ml⁻¹) for 5 days. ERK, extracellular signal-regulated kinase; OG-MEFs, Oct4-GFP-MEFs.