Understanding:
• Cyclins are involved in the control of the cell cycle
Mechanism of Cyclin Action
Cyclins are a family of regulatory proteins that control the progression of the cell cycle
Cyclins activate cyclin dependent kinases (CDKs), which control cell cycle processes through phosphorylation
- When a cyclin and CDK form a complex, the complex will bind to a target protein and modify it via phosphorylation
- The phosphorylated target protein will trigger some specific event within the cell cycle (e.g. centrosome duplication, etc.)
- After the event has occurred, the cyclin is degraded and the CDK is rendered inactive again
Cyclin Expression Patterns
Cyclin concentrations need to be tightly regulated in order to ensure the cell cycle progresses in a proper sequence
- Different cyclins specifically bind to, and activate, different classes of cyclin dependent kinases
- Cyclin levels will peak when their target protein is required for function and remain at lower levels at all other times
