It also targets S and M-phase (S/M) cyclins for destruction, which inactivates S/M cyclin-dependent kinases (Cdks) and allows the cell to exit from mitosis.

[8] Hartwell found mutants that did not enter anaphase and thus could not complete mitosis; this phenotype could be traced back to the CDC20 gene.

[9] However, even after the biochemistry of the protein was eventually elucidated, the molecular role of CDC20 remained elusive until the discovery of the APC/C in 1995.

Near its C-terminus it contains seven WD40 repeats, which are multiple short, structural motifs of around 40 amino acids that often play a role in binding with larger protein complexes.

In between these phosphorylation sites, which play regulatory roles, are the C-box, the KEN-box, the Mad2-interacting motif, and the Cry box.

The APC/C is a large E3 ubiquitin ligase, which triggers the metaphase to anaphase transition by marking select proteins for degradation.

S/M cyclins activate cyclin-dependent kinases (Cdks), which have a vast array of downstream effects that work to guide the cell through mitosis.

Their concentration rises during G1, activating G1/S Cdks, which in turn phosphorylate Cdh1 and gradually relieve the inhibition on S/M cyclins.

This checkpoint ensures that anaphase proceeds only when the centromeres of all sister chromatids lined up on the metaphase plate are properly attached to microtubules.

In fact, these three proteins, together with CDC20, likely form the mitotic checkpoint complex (MCC), which inhibits APC/CCdc20 so that anaphase cannot begin prematurely.

For gastric and pancreatic cancers, higher levels are correlated with tumor size, histological grade (the abnormality of the cells), and metastases to the lymph nodes.