Figure 7.—

Working model highlighting the mutual antagonism between the SAC and APC/C^Cdc20. (A) In the wild type, SAC engagement inhibits APC/C^Cdc20 activity; APC/C^Cdc20 reciprocally negatively regulates the SAC. Increased APC/C^Cdc20 activity is required to turn off the SAC and allow sister chromatid segregation and M phase exit. (B) In conditions where APC/C^Cdc20 activity is low, the negative regulation from the APC/C^Cdc20 is weakened, which results in a substantially prolonged engagement of the SAC, and hence increased M phase duration.