Time course of Rb phosphorylation in BLIN-2. Lanes 1 through 4, BLIN-1 and BLIN-2 were cultured for 18 hours and analyzed for Rb expression/phosphorylation as described in the Fig 10 legend. Lanes 5 through 9, BLIN-2 cells from lane 4 were replated on fresh BM stromal cells and reanalyzed at the times indicated for Rb expression/phosphorylation. The blot was restained with mouse antihuman β tubulin to control for equal protein loading.