Depletion of Aki1 induces spindle checkpoint arrest. (A) Percentage of mitotic cells in control or Aki1-2 siRNA–treated cells. Error bars represent SD of triplicate experiments (2,000–2,500 total cells were scored per condition). (B) HeLa cells were transfected with control or Aki1-2 siRNA. Cell lysates were immunoblotted with the indicated antibodies. (C–F) HeLa cells were transfected with control or Aki1-2 siRNA and costained for α-tubulin (α-tub; green) and BubR1, CENP-E, phospho-Ser¹⁰–histone (P-his), or cyclin B1 (red). (G) HeLa cells were transfected with control or Aki1-2 siRNA. Cell viability was measured using the cell viability assay. (H) HeLa cells were transfected with control or Aki1-2 siRNA. Cell lysates were immunoblotted with the indicated antibodies. Error bars represent SD of triplicate experiments. Bars, 5 µm.