INTRODUCTION
Major improvement of the model:
The previous model of the budding yeast (Chen et al., 2000) gives an adequate description of the Start transition, but, since it was published, many more molecular details about the Finish transition have come to light. Also in that paper, Clb2-kinase was assumed to activate Cdc20 directly, making the checkpoint protein Mad2 essential for cell viability, which is contrary to observation.
Here we introduce an intermediary enzyme, IE, that provides a time delay between Clb2 activation and Cdc20 activation, such that Mad2 is no longer an essential protein. The new model also accounts for how the MEN pathway facilitates Cdc14 release from the RENT complex and how the spindle assembly checkpoint impinge on the cell cycle engine.
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