lncreased risk of slippage upon disengagement of the mitotic checkpoint
Fig 5
Dynamics of nocodazole washout upon Mad2 overexpression.
A) Bifurcation diagrams showing the effect of increasing the Mad2 levels to 105%, 115% and 125% of Wild Type levels. Wild type in black. Equations in S1 Text, and parameters in Table 2. B) Barplots show percentages of simulated cells adapting or exiting, where adaptation is defined as APC/C activation with at least one unattached kinetochore. Reactions in Table 3, parameters in Table 2, initial conditions in Table 1 (checkpoint ON). C) Histogram of APC/C activation time in in simulated cells adapting (purple) or exiting (green). Details of simulations as in panel (B). D) Comparison of Clb2 degradation time (experiments) and APC/C activatiom time (simulations) in wild-type and GAL1-MAD2 cells. In the experiments (right), cells growing in YPRG are arrested in G1 and released in nocodazole for 240 minutes, when nocodazole is removed from the media. Cells carry Clb2-mCherry to record Clb2 degradation time. Only cells fully degrading Clb2 are included (see S2A Fig; 95% in wild-type, 87% in GAL1-MAD2). Simulations (left) produced as described in panel B. E) Percentage of cells that missegregate chromosome V. Cells growing in YPRG are arrested in G1 and released in nocodazole for 180 minutes, when nocodazole is removed from the media. Cells carry tetR-GFP/tetO construct to keep track of chrV segregation, and Htb2-mCherry to score nuclear division time. Cells that do not undergo nuclear division are excluded from this barplot (see S5F Fig). Missegregation is defined based on 5 frames (50 minutes) around nuclear division time. A cell is marked as missegregating chrV if after nuclear division either the two GFP dots end in the same cell or only one GFP dot is visible (see S5D and S5E Fig). For statistical comparison we used an exact Fisher test, where the contingency table has wild-type or mutant cells versus correct or wrong segregation of chrV (p-value = 1.3 10-4).