L04: Cell proliferation Flashcards
What are the 4 main phases in the cell cycle
- G1
- S phase
- G2
- M phase
What steps are known as the interphase
- G1
- S phase
- G2
What does an cdk stand for
Cyclin dependent kinase
How are cdks regulated
By cyclin levels
What do cdks do
They are kinases so they phosphorylate proteins
What are the main checkpoints in the cell cycle
Restriction point
G1/S checkpoint
G2/M checkpoint
M checkpoint
What does the restriction point do
If there are no growth factors, restriction point takes the cells into the G0 phase, this is where most of the cells rest.
What does the G1/S checkpoint do
Checks for DNA damage before the DNA is replicated
What does the G2/M checkpoint do
Checks if there is any DNA damage and checks if there is enough nutrients
What does the M checkpoint do
Checks if spindle is attached onto the kinetochore of chromosomes in the metaphase stage
How is G1/S checkpoint regulated
P53 checks for damage and increases in level if there is damage. P21 also increases and inhibits cdks from phosphorylating proteins . This gives time for DNA damage, if the damage is severe apoptosis occurs.
How is the restriction point regulated
PRB binds to transcription factors when there is no growth factors. This stops cdks from phosphorylation gene transcription factors so the cell cycle does not continue
How does growth factor signalling pathway work
1) growth factors bind to tyrosine kinase receptors
2) dimerisation occurs when the receptors phosphorylates itself
3) G protein called RAS becomes activated
4) RAS activates a kinase cascade reaction
5) gene transcription factors become regulated in the nucleus
How can mutation in the growth factor signalling cause tumours
- tyrosine kinase receptors can become oncogenic so it is always active and cell proliferation occurs
- Ras protein can become oncogenic so cell proliferation occurs constantly
- gene transcription factors can become oncogenic so cell proliferation occurs
What is prb
Tumour suppressing protein
