Cyclin A2 degradation during the spindle assembly checkpoint requires multiple binding modes to the APC/C

Nat Commun. 2019 Aug 27;10(1):3863. doi: 10.1038/s41467-019-11833-2.


The anaphase-promoting complex/cyclosome (APC/C) orchestrates cell cycle progression by controlling the temporal degradation of specific cell cycle regulators. Although cyclin A2 and cyclin B1 are both targeted for degradation by the APC/C, during the spindle assembly checkpoint (SAC), the mitotic checkpoint complex (MCC) represses APC/C's activity towards cyclin B1, but not cyclin A2. Through structural, biochemical and in vivo analysis, we identify a non-canonical D box (D2) that is critical for cyclin A2 ubiquitination in vitro and degradation in vivo. During the SAC, cyclin A2 is ubiquitinated by the repressed APC/C-MCC, mediated by the cooperative engagement of its KEN and D2 boxes, ABBA motif, and the cofactor Cks. Once the SAC is satisfied, cyclin A2 binds APC/C-Cdc20 through two mutually exclusive binding modes, resulting in differential ubiquitination efficiency. Our findings reveal that a single substrate can engage an E3 ligase through multiple binding modes, affecting its degradation timing and efficiency.

Publication types

  • Research Support, Non-U.S. Gov't
  • Video-Audio Media

MeSH terms

  • Amino Acid Motifs / physiology
  • Anaphase-Promoting Complex-Cyclosome / metabolism*
  • Anaphase-Promoting Complex-Cyclosome / ultrastructure
  • CDC2-CDC28 Kinases / metabolism
  • CDC2-CDC28 Kinases / ultrastructure
  • Cdc20 Proteins / metabolism
  • Cdc20 Proteins / ultrastructure
  • Cell Cycle Proteins / metabolism
  • Cell Cycle Proteins / ultrastructure
  • Cryoelectron Microscopy
  • Cyclin A2 / metabolism*
  • Cyclin A2 / ultrastructure
  • HEK293 Cells
  • Humans
  • Intravital Microscopy
  • M Phase Cell Cycle Checkpoints / physiology*
  • Models, Molecular
  • Protein Binding / physiology
  • Proteolysis
  • Spindle Apparatus / metabolism
  • Substrate Specificity / physiology
  • Ubiquitination / physiology*


  • CCNA2 protein, human
  • Cdc20 Proteins
  • Cell Cycle Proteins
  • Cyclin A2
  • CDC20 protein, human
  • Anaphase-Promoting Complex-Cyclosome
  • CDC2-CDC28 Kinases
  • CKS2 protein, human