Mitosis and Checkpoints Flashcards
what do Gap phases of the cell cycle allow for?
Time for cell growth and monitoring of external environment, and assessment of cell condition
When are CDKs present in the cytoplasm?
Always, just not always in an active state
How are CDKs activated?
By binding with cyclins
How is CDK1 partially activated?
cyclin B builds up and binds, this frees up the T loop
What cyclin activates CDK1?
Cyclin B
How is CDK1 fully activated?
- CAK phosphorylates T loop
Give an example of the action of active CDK1
Causes nuclear lamina to breakdown
How does wee1 regulate CDK1?
- wee1 phosphorylates Tyr15 on CDK subunit
- This inhibits kinase activity
How does Cdc25 regulate CDK1?
It is a phosphatase which removes the inhibitory phosphate added by wee1
When fully active what does CDK1 do to wee1?
It phosphorylates and inhibits wee1
When fully active what does CDK1 do to Cdc25?
It stimulates it’s activity
What regulates Cdc25?
- CDK1
- Polo like kinase
How does the cyclin kinase inhibitor inhibit CDK2-cyclin A?
It acts as a lock and ratchet and inactivates the complex by blocking it from targeting substrates
How are cyclins destroyed?
- Ubiquitinated by a specific ubiquitin ligase at appropriate points in the cell cycle
What controls cyclin ubiquitination?
Anaphase promoting complex
What are the 2 regulatory subunits of the APC?
Cdh1 and Cdc20
What does APc/Cdc20 target?
Mitotic cyclins at onset of anaphase to allow cell to transition to the next part of the cell cycle
What does APC/Cdh1 target?
- Mitotic cyclins present at G1 to prevent the cell from immediately undergoing mitosis again
- Also targets Cdc20
How does CDK1/Cyclin B inhibit Cdh1 complex?
Via phosphorylation of Cdh1 subunit
What removes the inhibitory phosphorylation from Cdh1?
Cdc14
