Figure 6.

The SAC prevents cell lethality by chromosome mis-segregation. (A–C) SAC is required for cell viability under conditions of histone depletion. The heterodimer Mad2/Mad1 (A), a functional kinetochore (B) and Aurora kinase (C) are required for t::HHF2 growth, as determined by synthetic growth defects of t::HHF2 and mad2Δ, mad1Δ, ndc10-1 or ipl1-321. (D) SAC prevents chromosome mis-segregation in cells partially depleted of histones. Chromosome segregation was followed in cells harboring an array of tetO sites labeled with tetR-GFP at 1.4 kb from the centromere. Asynchronous wild-type and G::HHF2 cultures were shifted from 2% galactose to 0.05% galactose medium for 4 h, and the fate of chromosome IV was followed by fluorescence microscopy in anaphase cells (as determined by DAPI staining). The right panel shows images of proper (one dot in the mother and one dot in the bud) and incorrect (both dots in either the mother or the bud) chromosome segregation. A total of 90–100 cells were analyzed for each strain and experiment. The average and SEM of three independent experiments are shown.