Expression of Ezh2 in MEFs. (A) At first MEFs showed rapid proliferation, but senesced after 8 population doublings. (B) RT-PCR analysis of young (p1) and aged (p5) MEFs. (C) Protein levels of Ezh2 in untreated MEFs at passage 1 and 9. (D) Schematic representation of retroviral vectors used to overexpress Ezh2. (E) Detection of Ezh2 protein in MEFs transduced with control and Ezh2 vector at different passages after transduction. (F) Relative expression of Ezh2 mRNA in MEFs transduced with the control vector (▪) or with the vector containing Ezh2 () at different passages after transduction. Expression levels of Ezh2 were determined by quantitative PCR and calculated relative to MEFs transduced with control at passage 1 after transduction. (G) Growth of MEFs after retroviral transduction (control, ▪; Ezh2, .