FIGURE 8.

Tyr-296 is required for a stable Cbp-Csk interaction and tumor-suppressive function of Cbp. A, whole cell lysates (WCL) from A549 cells and Cbp-expressing wild-type cells, Y296F mutant, and Y296F/Y314F double mutants were immunoblotted with the indicated antibodies. Cbp was then immunoprecipitated (IP) from whole cell lysates with anti-Cbp and then immunoblotted with the indicated antibody. Asterisks indicate the location of the immunoglobulin. B, effects of the expression of Cbp and its YF mutants on the tumor growth of A549 cells were examined using colony formation assays in soft agar. Colonies were stained with 3-(4,5-dimethylthiazol-2–2-yl)-2,5-diphenyltetrazolium bromide 10 days after plating. The colony numbers per cm² are presented as mean ± S.E. from three independent experiments. C, effects of the expression of Cbp and another mutant, AASAA, on the tumor growth of A549 cells were examined as described in B. The mutated amino acids are shown in bold letters in the sequence above the graph.