Anaphase-promoting complex
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Anaphase-promoting complex (APC) is a complex of several proteins which is activated during mitosis to initiate anaphase. The APC is a ubiquitin ligase that marks target proteins for degradation by the proteasome. It indirectly triggers the degradation of cohesin, the protein complex that attaches sister chromatids to each other. This allows them to separate in the manner characteristic of anaphase. The APC also marks the mitotic cyclins for degradation. This disassembles the MPF and thereby promotes the exit from mitosis.
The activity of the APC is inhibited by the spindle checkpoint when not all kinetochores are properly attached to the mitotic spindle.
There are two forms of the APC which target different sets of proteins and which are regulated differently. One, which is active early in mitosis and is responsible for triggering anaphase onset, contains Cdc20. The other, which is active later and drives exit from mitosis, contains Hct1 instead.