The Cell Cycle Flashcards
What are the 4 stages of the cell cycle?
G1
S
G2
M
What is the function of the M phase?
Make sure the chromosomes are attached at the appropriate locations
When are cells quiescent (inactive)?
G0
What are the checkpoints of the cell cycle?
G1/S checkpoint
S checkpoint
G2/M checkpoint
M checkpoint
What is the function of G1?
Cells undergo the cell cycle in the presence of growth factors. G1 is involved in commitment and restriction, ensures there I should enough growth fa tor for Thebes whole cycle.
What two types of instability are involved in cancer?
Genomic instability
Chromosomal instability
What two homologise are needed for replication and mitosis?
CDC28 and CDC2
What protein is involved in Sea Urchin and Xenopus Oocyte cell division?
Cyclins
What is M-phase Promoting Factor (MPF)?
A cyclin dependents protein kinase
Consists of:
- CDC2 (catalytic subunit)
- Cyclin B
What is the experiment for MPF?
Oocyte is treated with progesterone and stats to divide
Took the cytoplasm of the Oocyte and inject it into an Oocyte G2 arrested cell
They progress into M phase
Describe the cyclin-dependent protein kinase
1) cyclin binds to an inactive protein kinase
2) protein kinase is activated
3) binds to substrate
4) phosphorylate substrate
What is another name for MPF?
Cdk1-CyclinB
When are Cdk1-CyclinB levels high?
During M phase
When are Cdk1-CyclinB levels low?
During S phase
Explain CyclinB patterns in the cell cycle
Increase gradually and then drop after M phase
What CDKs and cyclins are present in G1?
Cyclin D1-3
CDK4 and 6
What CDKs and cyclins are present in late G1?
Cyclin E
CDK2
What CDKs and cyclins are present in S-M?
CyclinA
CDK1 and 2
What CDKs and cyclins are present in G2-M?
Cyclin B1 and B2
CDK1
Name a transcription factor involved in genes required for DNA synthesis
E2F-DP1
What’s controls E2F-DP1?
Retina blastoma proteins (RB) - negative regulator
What does the repressor complex contain?
RB
HDAC
SNF
SWI
How is the repressor complex released?
Phosphorylated at two locations on the RB
What is RB?
A tumour suppressor involves in a rare eye cancer
What can RB be targeted by to get cancer?
DNA tumour viruses e.g. SV40
Types of CDK inhibitors
INK4 family (inhibitors of kinase 4) - G1 phase inhibitors CIP/KIP family - S phase inhibitors
Roles of CDK inhibitors
Lineage-specific roles
Roles in regulating stem cell proliferation
p16 regressed epigenetically and reactivated during senescence
What is senescence?
Perminant withdrawak from the cell cycle into G0
How do growth factors start the cell cycle?
Activate signalling cascades which leads to transcription of Cyclin D (mitogen dependent)
What does Cyclin D interact with?
CDK4 and 6
P27KIP1
Effect of p27 on Cyclin D, CDK4 and 6
No effect, it does not inhibit them
Acts as a scaffolding protein
What do CyclinD-CDK4/6 do?
Isolate p27KIP1 and phosphorylated RB
What does cyclinD-CDK4/6-dependent phosphorylation of RB cause?
CyclinE expression
Function of CyclinE/CDK2
Further phosphorylated RB causes expression of genes for DNA synthesis
Phosphorylated p27KIP1 to target it for degradation
(Mitogen independent)
What are the oncogenes in the ERK pathway?
Receptor tyrosine kinase
Ras
Raf
CyclinD1
Which Cyclin does the ERK pathway cause expression of?
CyclinD1
Effect of p27 on CyclinE-CDK2?
Inhibits it
What does p16INK4A
CDK4/6
What cancers are related to mutations in?
Melanoma
Pancreatic cancer
What is the inhibitor of Mdm2?
P19ARF in mice
P14ARF in humans
What is the function of Mdm2?
Inhibit p53
What is the function of p53 on Mdm2?
Activates it, negative feedback loop
What does p53 regulate?
P21
Name two growth arrest genes
14-3-3 sigma
What are all of the types of things p53 can do?
Repair
Apoptosis
Growth arrest
Angiogenesis block
What kinases are involved in inhibiting Mdm2 due to DNA damage?
ATR
ATM
What kinase is involved in inhibiting Mdm2 due to UV damage?
ATR
What inhibitor inhibits Mdm2 due to oncogenes?
P14ARF
What complex causes c-Myc?
Smad4
Phosphorylated Smad3 x2
P107
E2F4/5
What are Smad3 Smad4 complexes
Transcriptional regulators of TGFbeta signalling
Where do p107 and E2F4/5 bind?
Smad response element
What do phosphorylated Smad3 x2 and Smad 4 bind to under p15 induction?
Fox
C/EBPbeta
What do phosphorylated Smad3 x2 and Smad 4 bind to under p21 induction?
FOXO - inhibited by PI3K and FoxG1
RUNX3
Through MAPK signalling RUNX3
Inhibitor of p15 and p21
c-Myc
TGFbeta transcriptions factor inhibitors
p21WAF1
p15INK4B
What cancer is HPV related to?
Cervical cancer
How does HPV cause cancer
1) expression of mutant gene E7 in the G1 phase which binds to RB.
2) RB releases the E2F-DP1 complex
3) progression into cell cycle
4) E6 binds to p53 and targets it for degradation
Pathways regulating senescence-mediated arrest
Telomere erosion Oncogene overexpression ROS mediated DNA damage Mitochondrial dysfunction Inflammation
4 protein kinase which control G2 and M
CDK1
CDK7
PLK1
Aurora A
What is the inactive form of CDK1?
T14 phosphorylation by MYT1
Y15 phosphorylation by WEE1
What does the dephosphorylation of T14 and Y15 cause?
Activation of CDK7 through binding to Cyclin H and allows phosphorylation of T161
Effect of DNA damage in the G2/M checkpoint
1) ATM activated (activate so p53)
2) Chk2 activate d (activates p53)
3) Cdc25 phosphorylated
4) Cdc25 binds to 14-3-3sigma protein
5) Cdc25 sequestered into the cytoplasm by 14-3-3
What ubqituitin ligand polyubiquitinates Cyclin B?
APC/C
Inhibitor of APC/C
SAC
What two CDKs are needed to make a a sterile rat?
CDK 1 and 4
Technique used to measure the cell cycle
Flow-activated cell sorter (FACS)
How does a FACSIMILE work?
1) grow cells on a dish
2) fix cells
3) harvest cells
4) add propidium iodide and incubate
5) calculate the relative amound of fluorescence
Function of propidium iodide
DNA intercalator
Binds to DNA in cells and adds fluorescence
