FIGURE 4.
Cyclin A kinase activity and p27 levels are changed in an ST-dependent manner in suspended cells. A, SV40- and DL888-infected wild type (WT) and p27 knock-out (p27D51) cells were cultured on plastic (black bars) or in suspension (white bars) for 24 h. Cells were subsequently labeled with either tritiated thymidine for 2.5 h (top) or BrdU (bottom) for 1 h. The values were obtained from the average of two experiments done in triplicate with one of the cell lines; however, all cell lines behaved similarly. Error bars indicate S.D. B, cyclin A- and CDK2-associated histone H1 kinase activity was measured (top). Expression of p27, cyclin A, and CDK2 was determined by immunoblot (IB) (bottom). This image is representative of the data obtained from one of the three cell lines for each genotype; however, all cell lines behaved similarly. IP, immunoprecipitation; SV, SV40; DL, DL888.