Figure 1.

Effect of TNP-470 on pRB phosphorylation, cyclin E-Cdk2 activity, and expression of cyclin E and Cdk2. HUVECs were synchronized by density arrest and replated at low density in the presence (+) or absence (−) of TNP-470 (10 nM), and harvested as described in Materials and Methods. (A) Western blot analysis of immunoprecipitated pRB. (B) In vitro kinase assay for cyclin E-dependent kinase activity. Samples were immunoprecipitated from lysates by using an anti-cyclin E Ab. Histone H1 was used as a substrate in the kinase reaction. (C) Western blot analysis of Cdk2, cyclin E, and actin expression levels.