导图社区 Cell cycle kinases
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Cell cycle kinases
Cellcycle kinases cancerMarcos Malumbres MarianoBarbacid Celldivision mammaliancells proteinkinases regulateprogression through variousphases cellcy
编辑于2022-06-14 21:40:38- cell
- Cell cycle …
- Anaphase…
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- regulation
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Cell cycle kinases
Classification
Gouping by Check points (human)
In yeast
Cdc2=Cdk1
Cdc28=Cdk2
A general diagram
diagrams of Check points
A diagram for the molecular mechanisms of DNA damaging check points
G1-S
>ristriction point
ristriction point
the point that cell is irreversible commited into the S phase
So G0 phase can be viewed as somewhere above this point
CyclinD-CDK4/6
The experiment
BrdU is a thymine analog, it incorporates into the nucleus only when DNA synthesis
about 14-16 hours
ristriction point>S
CyclinE-CDK2
about 6-8 hours
S-G2-M
CyclinA-CDK2
Also called S phase cyclin complex
Mitosis
The overall feed back loop
Prophase+Metaphase
CyclinB-CDK1(MPF)
full name
maturation promoting factor
Modules (molecules) linked
Nuclear envolope breakdown
MPF phosphorylates Lamins
Lamin network is nuclear lamina, which locates in the inside of the nuclear membrane
phosphorylations on specific serin residues depolarize lamin, it leads to the breakdown of the nucleus envolope.
Chromatin condensation
MPF phosphorylates and activates condensins
Cohesin glues the sister chromatids together at the centralmere region
Conhensin holds the supercoil of DNA to compact the chromatin into chromasome.
Fragmentation of Golgi and ER
MPF phosphorylates GM130
Spindle formation
MPF destabalize microtubule by phosphorylating the inhibitory site of myosin light chain
this also delayed cytokinesis
Some times it could be Cyclin A
Cyclin A/B-CDK1 is increased in late G2
Anaphase-telophase
APC/C
full name
Anaphase promoting complex or cyclosome
It is an ubiquitiligase rather than kinase
ubiquitin ligase (E3)
It responses to the rest of cell cycles other than CDK
Modules linked
Metaphase to anaphase
Separation of sister chromatids
extra information
How the kinetochor proteins attached to the kinetochor microtubules?
What kinds of spindle microtubules are there?
What is the position of the cohesin?
Cdc20 binds and targets APC to polyubiquitinates anaphase inhibitior(securin), then proteosome degredates the labbled anaphase inhibitor, anaphase inhibitor inhibits separase. The destroy of it activates seperase, which cleaves scc1. scc1 links smc1 and smc3, which they togeter forms cohesin.
The binding of Cdc20 to the APC is also mediated by the mitotic CDK
Late anaphase
Late anaphase activates cdc14, cdc 14 is a phosphatase, it dephosphorylates Cdh1, cdh1 is an activator of APC, the dephosphorylation of Cdh1 activates the APC-Cdh1 complex, activated APC-cdh1 polyubiquitinates mitotic cyclin(cyclin B), proteosome degredates polyubiquitinated mitotic cyclin(cyclin B). Cyclin B binds and activates CDK1 (MPF), The degredation of cyclin B will inactivates MPF and trigures the telophase
Cdc14 locates at the spindle possition check point, it is only activated when all the chromosomes have separated properly.
This ensure the complete set of chromosomes is distributed accurately in the daughter cells.
In the chromosome segregation checkpoint, the small GTPase Tem1 controls the availability of Cdc14 phosphatase
telophase
Reversion of MPF's effect
APC dephosphorylate all the targets of MPF
leads to
choromosomes decondense
Nuclear envolope reforms
Golgi, ER reconstruct
Nucleoli reassemble
picture
Cytokinesis(ATP-driven contractile machinary)
targets
actin, myocin II (myocin light chain)
They form a contractical ring beneath the membrane
The position of Mitotic spindle determines the position of the contractical ring
mechanism
contraction
CuclinB-CDK1 phosphorylates the myosin light chain at the inhibitory site. So, dephosphorylation of it by APC will makes the contractical ring to contract, this pinches the cell into two.
recovery
After division, CyclinB-CDK1 again phosphorylates inhibitory subunit of myosin, causing dissociation of myosin from actin filaments and inactivating the contractile machinery.
Subsequent dephosphorylation allows reassembly of the contractile apparatus for the next round of cytokenisis.
G1
CyclinE-Cdk2(G1-S check point) phosphorylates cdh1, this inhibits its activation on APC, so APC is inactivated
The mitotic cyclin(cyclin B) accumulates during interphase, finally it stimulates the next round of mitosis
regulation
Grouping by the changes
CDCs?
Cdc20
activates APC (most important function)
Cdc25
It's a dual-specificity phosphatase, it removes inhibitory phosphate residues on certain CDKs, it control entry of S phase and mitosis
Cdc28
A CDK in buding yeast
Identification
through a set of screening of genes related to cell division
Phospho-modifications on CDKs/Cyclins
CDKs
Activating phosphorylation
Residue
Thr60 for CDK2(on T loop)
forces the T loop out of substrate binding cleft
Kinase
Phosphatase
PTPase for CDK2
In yeast, single strand breaks activate Rad3, Rad3 activates a cascade to activate PTPase
Inactivating phosphorylation
Residue
Tyr15 for CDK2(in ATP binding site)
negatively charged phosphate group repulses ATP binding
Kinase
Phosphatase
CDK phosphorylates and activates this phosphatase
Cyclins
Phosphorylation can targets it to proteolysis
usually siganl directed
phosphorylation states determine cyclin's subcellular locolization
For example, Cyclin D1 is localised to the nucleus during G1 phase and is distributed to the cytoplasm upon the onset of S phase.
Ub-mediated proteolysis of Cyclins
DBRP
Working mechanism
DBRP recognizes distruction box of Cyclin A and B, it recruits ubiquitin. Ubiquitin ligase joints ubiquitins to the distruction box. When enough ubiquitins are ligated, proteosome degredates the ubiquitin labled cyclin.
Regulation
CDK phosphorylates and activates DBRP
DBRP phosphatase dephosphorylates and inactivates DBRP
The cyclins are commonly degredated, but the level of CDKs are constant
Synthesis of CDKs and Cyclins
E2F
Location
A transcription factor only exists in nucleus
Activity
E2F is a kinase, it phosphorylates and activates pRb and many tranbscription factors.
Regulation
Trough the MAP kinase cascade, Growth factors(mitogens) trigger the phosphorylation(activation) of Jun and Ros, they are transcription factors and they promote the synthesis of E2F
So growth factors can let the cell exit the G0 phase
pRb binds and inhibits E2F
In mid-Late G1, CyclinD-CDK4/6 partially phosphorylates pRb, the partial phosphorylation on pRb partially releases and activates E2F
Effects
Increases the transcription levels of Cyclin D and E, CDK 2 and 4.
early response genes
Those forms a positive feedback loop by fully phosphorylates pRb by cyclinE-cdk2 (make E2F's effect increases rapidly)
Here cyclin E will let cell to pass restriction pont and enter the S phase, the reason for the restiction point is irreversible is that E2F's activity is sustainable
Together with cyclin D and cyclin E, they Induces the synthesis of E2F transcription factors for the transcription of enzymes for DNA replication, Also includes the G1 cyclins and CDKs, it also increases the transcription of E2F it self.
cyclins can function independent of CDKs
cyclin D can interacts with more than 30 transcription factors and tanscriptional coactivators
Delayed response genes
How we can prove this?
The enzymes are essential for the synthesis of deoxynucleotides and DNA
Binding inhibition of CDKs
CIP(cyclin inhibitor proteins)
It can be viewed as the opposite of CDK activating proteins: cyclins
Its binding positions
Cyclin also offers structural element for the binding specificity with CKI
p21
Regulation
MRN detects double strand breaks, then MRN activates ATM and ATR. ATM and ATR phosphorylate ,activate, and stabalize p53, p53 is a transcription factor, it increases the transcription of p21
This system Check DNA damages for the G1/S check point, when the damage is too severe, p53 will triggers apoptosis pathway
when we lose both of copies of any proteins in this pathway, it can leads to cancer
An alternative pathway: chk(check point homologous)-cd25A pathway
ATM/ATR phosphorylates and activates chk, chk is a Thr/Ser kinase, it phosphorylates Cdc25 at the inhibitory site, which will stop it from path through the M-phase check point
ATR also can checks the Finish of DNA replication by binding to replication folk
It is degredated by the SCF( Skp1, Cullin, F-box protein complex), through ubiquitination
Effects
p21 binds and inhibits cyclinE-cdk2, and it blocks the cell from entering the S phase
It also inhibits the DNA replication, PCNA is a subunit of DNA polymerase theta
other factors might act with similar mechanisms
p27
p57
most of mamalian CDKs have corresponding CIPs
They act in S phase, anaphase, and telophase, they are all breaked down when the cell paththrough it
INK4(inhibitors of kinase 4)
also called p16, it interacts with CDK4 and CDK6, and it blocks the activation of them by cyclin D, this stops cell at the G1 restriction point
Targets of phosphorylation
Grouping by the effects
Nucleus envolope breakdown
target
Lamin
mechanism
phosphorylation depolarizes lamin, it leads to the breakdown of the nucleus.
Cytokinesis(ATP-driven contractile machinary)
targets
actin, myocin
mechanism
contraction
phosphorylation makes them to contract, this pinches the cell into two.
recovery
After division, CDK phosphorylates a small regulatory subunit of myosin, causing dissociation of myosin from actin filaments and inactivating the contractile machinery.
Subsequent dephosphorylation allows reassembly of the contractile apparatus for the next round of cytokenisis.
Tumour suppression
target
pRB
mechanism
phosphorylation on pRB releases E2F, which is normaly associated and inhibited by pRB