Figure 3
Premature senescence is characterized by Necdin downregulation. (A) Oncogene-induced senescence induced by RasV12 transduction of IMR90 cells caused a decrease in Necdin levels. Protein extracts were collected at the proliferation stage (day 4) and senescence (7 days after infection) (B) Stress-induced senescence generated by irradiation of IMR90 cells with 20 Gy also resulted in decreased Necdin level. Western blot analysis revealed protein modulation over time. (C-D) Necdin variation is not observed with transient arrest induced by serum starvation. (C) Flow cytometry analysis of IMR90 cells showed growth arrest after 24 hrs of serum starvation (0.1% FBS) compared to normal culture conditions (10% FBS). (D) Necdin protein levels of cells in normal or low serum conditions did not change.