Figure 2.
Activation of merlin at high cell density. (A) Wild-type merlin reduces growth in culture dishes but only at high cell density. RT4-D6P2T clones 54, 67, and L64P and vector control cells were seeded at low density (triplicates in 24-well dishes) and cultivated in the presence or absence of doxycycline. Cells per well were counted at 24-h intervals and the numbers plotted starting at 24 h after seeding. Standard errors are indicated. The insert shows a Western blot using an anti-Rb antibody (and anti-actin loading control) demonstrating that at high cell density (day 3 of culture) in the presence doxycycline, Rb is hypophosphorylated. Apparent molecular weights of phosphorylated, hypophosphorylated Rb and of actin are 112, 110, and 43kD, respectively. (B) Merlin reduces foci formation in culture dishes. Photomicrographs of RT4-D6P2T clone 67 cells in culture dishes at day 5 after seeding at low cell density in the absence or presence of doxycycline. Arrows in the left panel indicate large foci. Note absence of focus formation in the right panel.