FIG. 3.
Forkhead-induced upregulation of p130 does not contribute to inhibition of cyclin E-associated kinase activity. (A) MEFs infected as for Fig. 1A were lysed, and the amount of p130 in cyclin E-containing complexes was analyzed by Western blotting (WB) of cyclin E immunoprecipitates (IP). WCL, whole-cell lysate. (B and C) Primary wild-type MEFs and MEFs from p27kip1, p130, or p27kip1 p130 knockout mice were infected with a control or an FKHR-L1.A3-encoding retrovirus. At 24 h postinfection, proliferation was measured by BrdU incorporation (B) and cyclin E-associated kinase activity (act.) (C). Graphs show relative inhibition of proliferation by FKHR-L1.A3, as measured by these two assays, compared to proliferation with the control. Data are averages from three independent experiments. (D) Primary wild-type MEFs and MEFs from pRb, pRb p130, and pRb p130 p107 knockout mice were treated with 10 nM LY249002 for 16 h, and proliferation was assayed by BrdU incorporation.