Control of Cell Proliferation Flashcards
Why is the cell cycle controlled
To maintain genome integrity
Why is the cell cycle controlled
To maintain genome integrity
What does G1 involve
Growth + Prep for DNA replication
What does G2 involve
New DNA, organelles and cytoplasm for new cells
What does G1 checkpoint do
Ensure cell large enough to divide
If large enough, release growth factor
If no, switch to non-dividing state G0
What does the G1/S checkpoint do
Check damaged DNA
What does the G2 checkpoint do
Ensure DNA replication is successful
If not - cell death
What does the M checkpoint do
Ensure all chromosomes attached to mitotic spindle by kinetochore
If not - cell death
What enzymes regulate cell proliferation
Kinase
Cyclin dependent kinase - drives and accumulates during interphase
What happens to Cdk in G2
Enough Cdk to form M-Cdk which drives cell through mitosis
What happens to M-Cdk
Switches off by initiating process which destroys Cdk.
What does retinoblastoma protein do in the absence of growth factors
Bind to transcription regulators of genes to prevent cell cycle
What does retinoblastoma protein do in the presence of growth factors
Cdk phosphorylases pRB so it release binding of transcription factor regulators
What does p53 do
When it recognises damaged DNA, it activates transcription of p21 which inhibits Cdk so there is time to repair DNA
If too severe, p53 induces apoptosis
What are some of the consequences of checkpoint failure
Proliferation without growth factors
Replication of damaged DNA
Division of cells with wrong chromosome number
Gene instability = increase mutation = increase cancer
