Session 3 Cell Cycle & Apoptosis Flashcards
State the 4 cell cycle checkpoints
GO (in G1) G1 check (end of G1) G2 check (start of G2) M check (start of mitosis)
What are CDKs?
Cyclin-dependent kinases
Type of serine/threonine kinase
Phosphorylate substrates
What are cyclins?
Acute proteins degraded by ubiquitin-proteasome pathway
Which CDK and Cyclin is associated with each stage of the cell cycle?
G1 only - CDK4/6, Cyclin D
G1 & S - CDK2, Cyclin E
S only - CDK2, Cyclin A
M only - CDK , Cyclin B
Describe the role of P15, P16 & P21
They are Cyclin-dependent kinase inhibitors
P15 & P16 inhibit CDK4/6 & Cyclin D - so affect G1
P21 inhibits CDK2 & Cyclin E - so affect G1&S
Which protein regulates transition from G1 to S at the G1 checkpoint?
pRb
Explain how a cell progresses from G1 to S
Phosphorylation of Cyclin D & E and CDK 2,4 & 6 inactivated pRb, which normally represses transcription. The cell can then begin transcribing in S?
Which gene can be targeted to affect a cell’s progression from G1 to S?
E2F
What are the 5 stages of the cell cycle in order?
G1, S, G2, mitosis, cytokinesis
In which part of an intestinal villus is B-catenin usually turned off?
Top half
Explain how a B-catenin mutation leads to polyps
B-catenin constantly turned on. Activates Cyclin D, represses p16, promoting entry into S phase. Cells continue to behave as progenitors and proliferate rapidly.
Which protein senses DNA damage to halt entry in mitosis?
MPF - mitosis promoting factor
Which 2 ser/thr kinases are activated in response to DNA damage?
ATM, ATR
Name 4 things which phosphorylate P53?
Chek1, chek 2, ATR, ATM
Which ser/thr kinases relate to CHK1 & CHK2?
ATR CHK1
ATM CHK2
