Which kinase activates APC/C-Cdc20 to trigger the metaphase-anaphase transition?
Assembly and activation of APC/C-Cdc20 must occur only after CDK1 has driven mitotic entry, ensuring anaphase does not initiate prematurely. During G2, APC/C exists in unphosphorylated inactive conformation with weak affinity for Cdc20, while Cdc20 itself is kept inactive by CDK inhibitory phosphorylation and binding to checkpoint protein Mad2. Upon entry into mitosis, cyclin B-CDK1, the master mitotic kinase, phosphorylates multiple subunits including APC1 at loop region, APC3, and APC6, inducing conformational rearrangement exposing C-box binding groove. Polo-like kinase Plk1 adds further ph
Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 20: Mitotic Activation of APC/C.