Cell cycle regulation Flashcards
Cell cycle regulation at G1 (Cyclin type only)
Cyclin D, CDK4/6
cell cycle regulation at S
Cyclins E&A, CDK2
cell cycle regulation at G2
Cyclin A, cdk1
cell cycle regulation at M
Cyclin B, cdk1
How does Retinoblastoma protein regulate Entry to S phase?
In resting cell, Rb is hypophosphorylated thus attached E2K protein (inhibitor of cell cycle). But when Rb is hyperphosphorylated by Cyclin D and cdk4/6, it dissociates from E2K, then free E2K activates Cyclin E, A, thus cell enters S phase.
Which part of cell cycle does retinoblastoma control?
from G1 to S Entry
Which protein activates CyclinB-Cdk1 complex?
Cdc25C phosphatase
What does cdc25C phosphatase do?
CDK1 has activating and inhibitory phosphorylation on it. Phosphatase removes inhibitory phosphorylation of CDK1, thus enabling CDK1 to bind to Cyclin B, allowing cell to enter mitosis.
What part of cell cycle does CDC25C phosphatase regulate?
G2 to M entry
Role of p53 gene in cell cycle regulation (2)
- Regulating cell cycle (If DNA damage is repairable, it stops cellcycle by activating p21 transcription. (cdk inhibitor)
- If not repairable, apoptosis is initiated, activating Bax gene.
Role of Anaphase promoting complex (APC) (2)
It regulates activity during anaphase.
- When activated by Cdc20, it degrades securin by ubiquitylation.
- Then, separase gets activated, which cleaves cohesin complexes that joins sister chromatids together. Thus sister chromatids separate.
Also, ubiquitylation and degradation of M-Phase Cyclin B
What is the central regulators of the DNA damage checkpoint?
ATM and ATR
What happens at G1, S, G2 DNA check point regulated by ATM and ATR?
At G1, ATM & ATR activate p53 or p21, resulting in either apoptosis or halt of cell cycle.
At S, ATM & ATR activate BRCA1 gene, for repair of dsDNA breaks.
At G2, ATM&ATR inhibit cdc25C phosphatase, which usually activate cdk1.
3 tumor suppressor gene
p53
Retinoblastoma
BRCA1
