Figure 5. CSN6 impacts on p57 to regulate HER2-mediated cell proliferation, cell cycle progression and cell transformation. (A) p57 is induced in NIH3T3/HER2/tTA-p57 cell in the absence of tet. NIH3T3/HER2/tTA-p57 cells were treated with (+) or without (-) tet and the cell lysates were immunoblotted with indicated antibodies. (B) CSN6 expression antagonizes p57-mediated reduction of BrdU incorporation. NIH3T3/HER2/tTA-p57 cells were transfected with CSN6 and then treated without (-) tet. The cells were fixed for anti-BrdU staining. BrdU-positive cells were counted and presented as a bar graph. Error bars represent 95% confidence interval. (C) CSN6 expression hinders p57-mediated G₁ arrest. NIH3T3/HER2/tTA-p57 cells were transfected with CSN6 and then treated without (-) tet. The cells were analyzed by FACS for cell cycle distribution. The percentages of each cell cycle phase are presented as a bar graph. Error bars represent 95% confidence interval. (D) CSN6 expression compromises p57-mediated inhibition of cell transformation. NIH3T3/HER2/tTA-p57 cells were transfected with CSN6 and then treated without (-) tet. The cells were analyzed for anchorage-independent growth by soft agar colony formation assay. The numbers of colony formation are presented as a bar graph.