Research Paper Volume 1, Issue 6 pp 542—556

Figure 1. Oncogenic N-RAS^Q61K induces proliferative arrest and senescence of human melanocytes. (A) Human melanocytes were transduced with lentiviruses expressing N-RAS^Q61K or copGFP control. The efficiency of transduction was controlled with the co-expression of copGFP and was consistently above 90%. Cell proliferation (Ki67), chromatin condensation (DAPI), and the appearance of increased SA-β-Gal activity were analyzed and quantitated 15 days after infection. Percentage of cells positive for the indicated marker is shown in histograms, which correspond to the mean ± s.d. of at least two independent transduction experiments from a total of at least 300 cells. Cells enlarged to show DAPI-stained chromatin foci are indicated with arrows (bar =10 μm). LM, light microscopy (bar=100μm). (B) Human epidermal melanocytes infected with lentiviruses expressing N-RAS^Q61K or copGFP were stained with DAPI and antibodies to H3K9Me, 15 days post transduction (bar =10 μm). (C) Expression of the indicated proteins was determined by western blot analysis 15 days after infection of human epidermal melanocytes with lentiviruses expressing N-RAS^Q61K or copGFP control.