Figure 2.

Sgo2 is required for preventing cosegregation of sister chromatids and activating the spindle checkpoint in the absence of tension. (A) Quantification of cen2-GFP nondisjunction in sgo2⁺ nda3-KM311 and sgo2Δ nda3-KM311 cells after block at 20°C and release to 36°C. Error bars represent the SD of duplicate samples (each n > 100). Note that some cells segregate the DNA within one cell compartment because of the displacement of the nucleus relative to the septum. (B) The indicated strains were arrested at G1/S phase by adding HU at 25°C and released to 36°C. Prometaphase (SPB duplicated and securin/Cut2-positive) cells were counted at each time point (n > 150). Examples of Cut2-GFP and Sad1-GFP images at metaphase and anaphase are shown. Note that Cut2-GFP, but not Sad1-GFP at SPBs, disappears from the anaphase cell. (C) Live imaging of the indicated strains expressing Mad2-mCherry, Cut2-GFP, and Sad1-GFP. The numbers indicate elapsed time (in minutes). (D) Prometaphase length of single cells was measured for each strain. One bar corresponds to a single cell.