Cell Cycle Flashcards
What can help control the cell cycle
rounds of protien degredation and protien synthesis that either move the cycle forward or stop it
Phosphorylation events
Regulatory protiens
What are some key regulatory protiens of the cell cycle
Tumor suppressors and oncogenes (tumor causing)
What are the two phases in the cell cycle
S phase: dna synthesis where the genome is replicated
M phase: mitotic phase where the chromosomes get separated to daughter cells
How can the s phase (dna replication) be monitored
By adding in 3HT
if the length of the cell cycle is known, the length of that s phase can be calculated by the percent of cells labeled with 3HT
IDK
How can dna be analyzed with a fluorescence activated cell shorter (FACS)
The cells are stained with a dye called propidium iodide the floureces when the cell bind to dna
The amount of flourense is equal to the amount of dna in the cell
IDK
Slide 10
Idk
How is entry of the cell into the M PHASE triggered
By a protein kinase called the maturations promoting factor (MPF)
What is the MPF
It has two subunits
A kinase and a regulatory cyclin subunit
When there’s higher cyclin concentration, the kinase if the MPF is activated
This drives mitosis forward
What happens when cyclin is low
What if high
Low, the MPF kinase doesn’t have the cyclin subunit, it’s inactive
High, the MPF kinase has the cyclin subunit, it’s activated and entry to mitosis starts
What type of cells is MPF in
Mammalian
At what two points is the cell cycle controlled in yeast cells
The START (between g1 and S) and G2-m transition
In yeast cells what activated the cell cycle
The same kinase: cdk(also called cdc2)
Two different cyclin for the two diff points of control (g1/s cyclin and mitotic cyclins)
Explain how the activation of the cell cycle happens in yeast cells
Intially g1/s cyclins are produced and a complexing with the cdk
This activates the cell cycle
Eventually, the g1/s cyclins get degraded and the new mitotic cyclins complex with cdk to promote mitosis
Eventually these mitotic cyclins drop off again at the end of m phase
So basically round of cyclin degradation and synthesis control the cycle
What is used to activate and deactivate the kinases to control the cell cycle
CAK
WEE1
cdc25
What is CAK
Cdc activating kinase
It adds a phosphate to the thr161 on the cdk subunit to activate it
What is WEE1
A cdc inhibiting kinase
It adds a phosphate to the tyr15 to deactivate the kinase and stop mitosis
Cell is not wee anymore since not splitting
What is cdc25
A phosphatase
It removes the inhibitory phosphate from tyr15 on the cdk
This is the step that drive mitosis forward
What is cyclin d1
A cyclin that is made from the mapk pathway
Its key to start the cell cycle and is present in g1
What is special about the cdks and their cyclins
There a many different cyclins and specific pairings of these cycling to the cdks
What is the effect of a anticancer drugs on the cdks and cyckins
The drugs inhibit the cdk4 and cdk6 in the g1 phase
What is the retinoblastoma protien (pRB)
Protien that Controls the cell cycle
Represses the genes needed for S phase to start
If mutated there is abnormal cancer growth, so it is a tumor suppressor
when is pRB phosphorylated/dephisphorylated
When is it inhibited and activated
Phosphorylated: at end of G1
De: at end of m phase
Inhibited when phosphorylated,
Activate when dephosphorylated
Describe how pRB represses genes for a phase
In g1, the transcription factor E2F is bound to pRB
This is all at the promoter in the dna and represses the gene
Once CDK is activated, it phosphorylates pRB and the inactive pRB is released from E2F
The lone E2F on the dna turns into an activator and is now able to transcribe dna for s phase
What happens to E2F once the s phase is over
The pRB goes back to E2F to repress s phase until it’s needed again