Apc/c

Definition

The anaphase-promoting complex/cyclosome (apc/c) is a crucial multi-subunit E3 ubiquitin ligase that regulates the cell cycle by marking specific proteins for degradation. This process is vital during the transition from metaphase to anaphase in cell division, ensuring that sister chromatids are properly separated. By tagging proteins with ubiquitin, apc/c helps control the timing of the cell cycle and maintains genomic stability.

5 Must Know Facts For Your Next Test

1. apc/c is activated by the binding of co-activators such as Cdc20 or Cdh1, which are essential for its function in marking target proteins for degradation.
2. It plays a vital role in triggering anaphase by targeting securin for destruction, which allows separase to activate and cleave cohesin, facilitating sister chromatid separation.
3. apc/c also helps regulate the exit from mitosis by degrading cyclins and ensuring that CDK activity is downregulated, thus allowing the cell to progress to the G1 phase.
4. Failure in apc/c function can lead to improper chromosome segregation and is associated with various cancers due to its role in maintaining genomic stability.
5. The activity of apc/c is tightly regulated throughout the cell cycle, with different activators and inhibitors modulating its function to ensure accurate cell division.

Review Questions

• How does apc/c contribute to the regulation of the cell cycle, particularly during the transition from metaphase to anaphase?
  • apc/c contributes significantly to the regulation of the cell cycle by marking key proteins for degradation as cells transition from metaphase to anaphase. It targets securin for destruction, which releases separase to cleave cohesin, allowing sister chromatids to separate properly. This action is critical for ensuring that chromosomes are evenly distributed into daughter cells, maintaining genomic integrity.
• Discuss the importance of proper apc/c function and how its malfunction can lead to cancer.
  • Proper apc/c function is essential for accurate chromosome segregation during cell division. If apc/c malfunctions and fails to degrade target proteins effectively, it can result in errors during mitosis, leading to aneuploidy or chromosomal instability. Such abnormalities are commonly observed in various cancers, where disrupted regulation of the cell cycle contributes to uncontrolled cellular proliferation and tumor development.
• Evaluate how apc/c interacts with other proteins in the context of cell cycle regulation and what implications this has for cellular health.
  • apc/c interacts with several proteins, including co-activators like Cdc20 and Cdh1, which enhance its activity at different phases of the cell cycle. These interactions are crucial for targeting specific substrates for degradation, such as cyclins and securin. When these interactions are disrupted or when apc/c activity is compromised, it can lead to severe consequences for cellular health, including increased risk of cancer due to unchecked cell division and compromised genomic stability.

Related terms

Ubiquitin: A small protein that is attached to other proteins to signal their degradation by the proteasome, playing a key role in regulating protein turnover within cells.

Cyclins: Proteins that regulate the cell cycle by activating cyclin-dependent kinases (CDKs); their levels fluctuate throughout the cell cycle, controlling progression through different phases.

Proteasome: A large protein complex responsible for degrading and recycling damaged or unneeded proteins tagged with ubiquitin, thus maintaining cellular homeostasis.