Slimb and E2F associate in vitro. GST-Slimb(176–510) can interact with E2F (lane 3) but not with another protein (luciferase, lane 1). GST alone does not interact with E2F (lane 2). Treatment of E2F with active alkaline phosphatase prevents binding to Slimb (lane 4). Binding is restored in the presence of the phosphatase inhibitor Na3VO4 (lane 5).