Lecture 10 Flashcards
1
Q
Cell Cycle Checkpoints
A
- Checkpoints ensure condition suitable for division
- Mediated by controlled activity of cyclin-dependent kinases(Cdks)
- Phosphorylate target proteins for cell cycle to progree -> require cyclins
2
Q
Cyclin-cdk
A
- Cdks present throughout all cell cycle stages
- Cyclins made and broken down at different cell cycle stages
- Cyclin-Cdk combination controls which target proteins are phosphorylated
- G1/S and S-Cdk target DNA helices
- M-cdk target lamins and microtubule-associated proteins
- One Cdk may work with multiple cyclins, but cyclins only work at one stage
- Polyubiquiantion marks cyclins for degradation -> Cdk not active
- APC/C and Cdc20 act on E3 ubiquitin ligase
3
Q
Cdk-Activating Kinase
A
- Cyclin absolutely required for Cdk activity by exposing T-loop
- CAK can phosphorylate Cdk to activate
- PP2A remove phosphorylation -> same target as Cyclin-Cdks -> involve in feedback loop with Cyclin-Cdks
4
Q
Cdk inhibitor proteins(CKI)
A
- CKI bind cyclin-cdk to inactivate
- eg. p27 and p21
5
Q
Inhibitory phosphorylation
A
- Inhibitory phosphorylation at different site from activating phosphate
- Wee1 kinase adds inhibitory phosphorylation
- Cdc25 remove inhibitory phosphorylation -> needs to be phosphorylated to be active
6
Q
Cells retained in G1 by Rb
A
- E2F transcription factor required for S phase gene expression
- Rb binds and inhibits E2F
- Rb inhibited by phosphorylation
7
Q
Myc
A
- Mitogens trigger production of Myc -> key transcription factor
8
Q
p53
A
- DNA damage induces p53 -> activates p21 expression -> p21 is CKI that inhibits G1/S-Cdk and S-Cdk