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#mitotic checkpoint

2 public questions tagged with this topic.

Cell Cycle Regulation

What happens if Cdc20 is inhibited?

Anaphase entry requires anaphase-promoting complex/cyclosome (APC/C) activated by co-activator Cdc20, which targets securin and cyclin B for proteasomal degradation via K11-linked polyubiquitination. Securin normally binds and inhibits separase, protease that cleaves cohesin subunit Rad21 holding sister chromatids together. When APC/C-Cdc20 destroys securin, liberated separase removes cohesin, allowing sister chromatids to separate toward opposite poles. If Cdc20 is absent, inhibited by MCC, or chemically blocked, APC/C remains inactive, securin and cyclin B persist, separase stays inhibited,

Ref: Peters, Nature Rev Mol Cell Biol 2006, APC/C and Cdc20; Sivakumar & Gorbsky, Nature Rev Mol Cell Biol 2015, Spindle Checkpoint.

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Cell Cycle Regulation

Which protein complex is responsible for delaying mitosis in case of spindle defects?

Accurate chromosome segregation requires that all kinetochores achieve amphitelic attachment to spindle microtubules from opposite poles and generate tension. Unattached or improperly attached kinetochores generate wait signal that delays onset of anaphase to prevent mis-segregation. This delay is enforced by mitotic checkpoint complex, abbreviated MCC, composed of Mad2, Bub3, BubR1 (Mad3 in yeast), and Cdc20. At unattached kinetochores, scaffold protein Knl1 is phosphorylated by Mps1, recruiting Bub1-Bub3 and Mad1-Mad2 complexes that catalyze conformational conversion of open Mad2 to closed f

Ref: Musacchio & Salmon, Nature Rev Mol Cell Biol 2007, Spindle Assembly Checkpoint; Lara-Gonzalez et al., Curr Biol 2012, MCC Functions.

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