Fig. 4. Constitutively active Plk1 causes nuclear translocation of Cdc25C. (A) The indicated forms of Myc-tagged Cdc25C, HA-tagged Plk1 (vector, WT or SDTD) and/or untagged cyclin B1 were expressed in HeLa cells. Fifteen hours after transfection, cells were fixed, followed by staining with anti-Myc and anti-HA antibodies. More than 200 cells were examined in each condition, and the percentages of the cells in which Myc-tagged Cdc25C was accumulated in the nucleus are shown. (B) Typical images of Myc-tagged Cdc25C (middle column) co-expressed with HA-tagged Plk1 (left column) and untagged cyclin B1 are shown with DAPI staining (right column). When S198,216A-Cdc25C was expressed, part of this mutant Cdc25C localized to the nucleus. Expression of SDTD-Plk1 and cyclin B1 did not enhance at all the nuclear localization of this mutant Cdc25C (data not shown).