FIGURE 3.

Tgfβ1, -2, and -3 induce p19^Arf and the Arf promoter in cultured MEFs in a manner that depends on TβrII. A–C, shown is a representative Western blot of lysates from wild type MEFs (A) and β-galactosidase (β-Gal) activity in Arf^lacZ/lacZ MEFs (B and C) showing the time course of Arf induction after 48 h of exposure to Tgfβ1, -2, or -3 (Τ1, T2, T3), BMP2, or vehicle (V). Induction by each Tgfβ protein was statistically significant when compared with respective vehicle (B and C, *), as was the slight repression by BMP2 (C, #) (p ≤ 0.0002 in each case). D, shown is a representative Western blot for the indicated proteins using lysates from Tgfbr2^fl/fl MEFs infected with either adenovirus encoding red fluorescent protein (RFP) or Cre recombinase and exposed to Tgfβ2 or vehicle for 48 h. Note that p19^Arf induction (lane 2 versus lane 1) is blunted after inactivation Tgfbr2 (lane 4 versus lane 3).