FOCAL POINT  David Morgan (left), Dan Lu (right), and colleagues (not pictured) describe how budding yeast ensure that proteins are degraded in the correct order during mitosis. By analyzing the disappearance of APC/C^Cdc20 substrates in individual yeast cells (right), the researchers find that the S phase cyclin Clb5 (gray) is targeted for degradation six minutes earlier than the chromatid cohesion regulator securin (red). This difference is maintained by multiple mechanisms that either promote or inhibit the substrate proteins’ direct or indirect association with the APC/C^Cdc20.

PHOTO COURTESY OF THE AUTHORS