Intro to cell cycle? Flashcards
What are the two main parts of cell cycle?
Interphase and mitosis
What is the interphase stage? And what phases is it made up of? What is the purpose of each stage?
It’s when chromosomes prepare for duplication and duplicate. G1,S,G2.
G1-growth and metabolic roles
S-chromosome duplication
growth and prepration for mitosis
What is the fastest stage in the cell cycle?
Mitosis
What are the periods found in mitosis and what is the purpose of each?
Prophase-The chromosomes will condense
Metaphase-The chromosomes will attach to spindles and move toward the center of the cell
Anaphase- Sister chromatids will seperate
Telophase- The chromosomes will decondense
What is cytokinesis?
Physical seperation of divided cells
When are cell in G0? What is G0?
The resting phase
Differntiated or deprived of nutirents
What is the purpose of checkponts and control in cell cycle?
To ensure that the cells divided with no errors and they are diploid
Who was awarded noble prize for discovering control mechanism in cell cycle? What are the conclusions of cell fusion experiments?
Hartwell, nurse, Hunt.
MPF contains factors that can induce chromosome condensation at any cell stage
But SPF has factors that only induce replication in G1 phase
What proteins are involved in controlling cell cycle?
CDK and cyclins
What period are cells sensitive to mitogens?
G1
How many cyclins, CDK, CDKI were identified in mammals?
13 cyclins, 8CDK,7CDKI
T/F
Cyclins and CDK the only proteins that change in the cell cycle
False
T/F
Cyclin D is cell type specific
True
How are cyclins turned off?
By ubiquination and degradation
What genes transcribe Cyclin D? And what CDK do they bind to? What stage of the cell cycle are they expressed?
AP-1, c-myc, NFKB.
cdk4,2,6,5
Early stages G0,G1, peaks near the end of G1
What do cyclinD/CDK4 act on and what does it induce? What is it’s effect in the cell cycle?
RB, it phosphorylates RB which releases it from E2 phase, it induces th eprogression of the cell to S phase and through the restriction point
When is cyclinE/CDK 2 expressed? And what is it’s effect in the cell cycle?
At the end of G1 and degrades 1/2 way through Sphase
T/F
cyclinE/CDK 2 has histone kinase activity
T
When is cyclin A expressed and when does it degrade? What does it bind to? Why is it important in the cell cycle?
At the end of Sp phase, at anaphase
CDK2,1
Initiation and progression of replication
When is cyclin B expressed and when does it degrade? What does it bind to? Why is it important in the cell cycle?
end of S phase, end of anaphase
binds to CDK
Needed for cell to enter mitosis
Give an example of phosphatase? When does it accumulate?
CDC25, M phase
What role does phosphorylation play in CDK and cyclin during cell cycle
It activates and inactivates activity and it’s important for nuclear localization
What is CDC 13 and what is it’s role?
It’s a type of cyclin B important in cell cycle control prevents the cell from moving from g2 to m phase
What brings the cyclins to their CDKS?
chaperone complex
What is P21 and how does it work? What is it used for normally?
P21- is a tumour suppressor that inhibits all CDK/cyclin complexes and DNA polymerase.
It is expressed durong differentiation
What are other cyclin kinase inhibitors?
P14, P15,P16, P18.
What is ARF and how does it effect P53? What activates ARF?
ARF is a tumour suppressor that activates P53 and P16 by inhibiting MDM2. Overexpression of c-myc and E2F
What does MDM2 do?
It ubiquitinates P53 and exports it out of the nuclease for degradation
Explain how P27 is induced and works and how it’s inhibited?
P27 would be induced by cell-cell contact and TGF-B
iT inhibits the cyclin E,D ,A complexes which inhibits RB phosphorylation. It is associated with migration
It is inhibited by AKT which phosphorylates it and it’ll be exported.
What are ways to target cancers using cell cycle proteins?
Chemotherapeutic- kinase inhibitor
Adeno reteroviral vector that overexpresses any of cyclin kinase inhibitor such as p21
antisense against cyclin D
What activates P53 molecularly?
ATM and ARF
What regulates the g2/m transition?
CHK1 phosphorylates CDC25 which will keep cdc2 in it’s inactive form
What does P53 produce when activated?
p21 and GADD45.
What does GADD45 do? What does P21 do?
It binds to PCNA and repairs DNA
While p21 inhibits PCNA induces apoptosis or a pause in the cell cycle progression
What regulates G1/S transition?
P53
