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. 1998 Oct 1;12(19):2997–3007. doi: 10.1101/gad.12.19.2997

Figure 8.

Figure 8

MEK activity is required for induction of p16Ink4a and senescence by Raf in IMR-90 cells. (A) Inhibition of MAP kinase activation and p16Ink4a expression by PD098059. Asynchronously growing IMR-90 cells expressing GFPΔRaf-1[YY]:ER were treated with either 10 nm 4-HT or an equivalent volume of ethanol (ETOH) for 4 days in the absence (DMSO) or presence of the MEK inhibitor PD098059 (PD, 25 μm) as indicated. The activity of p42/p44 MAP kinase and the expression of p42 MAP kinase and p16Ink4a were assessed by Western blotting with the appropriate antisera. (B) MEK activity is required for Raf-induced senescence in IMR-90 cells. Control (Babe) and GFPΔRaf-1:ER ([YY]- and [DD])-expressing IMR-90 cells were treated with various combinations of 4-HT (10 nm for [DD] and 3 nm for [YY]), PD (25 μm), or an equivalent volume of ethanol or DMSO for 6 days, and stained for SA–β-galactosidase activity.