Taxol induces loss of end-on microtubule attachments on a low number of kinetochores in metaphase cells. (A) Time-lapse recording of a taxol-treated metaphase cell that exits from mitosis. In this cell, Mad2-Venus disappears from the last kinetochore (red arrow in frame 00:00) shortly after addition of taxol. The cell exits from mitosis ∼15 min later and undergoes cytokinesis (red arrows in frame 22:45). Notice that because of stabilization of microtubules in taxol, chromosomes (seen as dark bodies in fluorescent background) do not move poleward but remain near the spindle equator during anaphase and telophase. (B) Time-lapse recording of a taxol-treated metaphase cell. In this cell, Mad2-Venus disappears from the last pair of kinetochores shortly after addition of taxol (red arrows in 00:00 and 01:40). Approximately 5 min later Mad2-Venus begins to accumulate at a different kinetochore (arrowheads in 05:20 and 07:15). This kinetochore is identified via correlative EM of this cell fixed shortly after 7:15. (C) Serial section (Sect.) EM demonstrates that the Mad2-Venus positive kinetochore completely lacks end-on microtubule attachments, and its electron-opaque corona partially encircles the centromere (arrows). In contrast, the sister kinetochore has a well-defined outer plate with several end-on attached microtubules (arrowheads).