Figure 6.

gdt1⁺ cells do not influence discoidin overexpression in gdt1⁻ cells. L8 and DAG cells were mixed at the indicated ratios and grown to a density of 1 × 10⁶ cells/ml. Cells were harvested and lysed and proteins were separated on a polyacrylamide gel. After blotting, the filter was incubated with the anti-discoidin antibody and then with an alkaline phosphatase-coupled secondary antibody and stained. At 1 × 10⁶ cells/ml discoidin expression is not detectable in DAG cells (100% DAG lane). Staining in the other lanes thus corresponds to increasing amounts of L8 cells. The increasing amount of discoidin corresponds approximately to increasing amounts of L8 cells, indicating that wild-type cells do not secrete an extracellular factor, which can compensate the overexpression phenotype of the mutant.