APC/C

Definition

APC/C, or Anaphase-Promoting Complex/Cyclosome, is a multi-subunit E3 ubiquitin ligase that plays a crucial role in the regulation of the cell cycle. It functions by tagging specific proteins for degradation, ensuring that cells progress through key transitions such as anaphase and mitosis. By targeting cyclins and other regulatory proteins, APC/C helps maintain proper timing and order of cell division, which is vital for cell health and function.

5 Must Know Facts For Your Next Test

1. APC/C is activated by co-factors like Cdc20 and Cdh1, which help target specific substrates for degradation during the cell cycle.
2. The primary role of APC/C is to facilitate the transition from metaphase to anaphase by degrading securin, which prevents premature separation of sister chromatids.
3. APC/C also plays a role in G1 phase by degrading cyclins, leading to a reduction in cyclin-dependent kinase (CDK) activity.
4. Dysregulation of APC/C activity can lead to various cancers due to improper cell division and genome instability.
5. APC/C activity is tightly regulated by phosphorylation and interaction with different proteins to ensure accurate cell cycle progression.

Review Questions

• How does APC/C contribute to the transition from metaphase to anaphase during cell division?
  • APC/C contributes to the transition from metaphase to anaphase by targeting securin for degradation. Securin normally inhibits separase, an enzyme that cleaves cohesin proteins holding sister chromatids together. When APC/C degrades securin, separase is activated, allowing for the separation of sister chromatids and progression into anaphase. This process is crucial for ensuring that chromosomes are accurately distributed to daughter cells.
• Discuss the implications of APC/C dysregulation in relation to cancer development.
  • Dysregulation of APC/C can lead to unregulated cell division and genomic instability, both of which are hallmarks of cancer. If APC/C fails to degrade cyclins or other regulatory proteins appropriately, cells may proceed through the cell cycle uncontrollably. This uncontrolled growth can result in tumor formation and the development of various cancers, highlighting the importance of precise control mechanisms like APC/C in maintaining cellular health.
• Evaluate how APC/C's regulation by phosphorylation and co-factors affects its role in the cell cycle.
  • The regulation of APC/C through phosphorylation and interactions with co-factors like Cdc20 and Cdh1 is essential for its functionality during different phases of the cell cycle. Phosphorylation events can either activate or inhibit APC/C's activity depending on the context within the cycle, ensuring it targets the correct substrates at the right time. This dynamic regulation allows APC/C to precisely control transitions such as metaphase to anaphase and G1 phase exit, demonstrating its critical role in maintaining orderly cell division and preventing errors that could lead to malignancies.

Related terms

Ubiquitination: The process of attaching ubiquitin molecules to a substrate protein, marking it for degradation by the proteasome.

Cyclins: Regulatory proteins that are essential for the progression of the cell cycle, whose levels fluctuate throughout different phases.

Cell Cycle Checkpoints: Control mechanisms in the cell cycle that ensure proper division and prevent errors such as DNA damage or incomplete replication.