Cell cycle and apoptosis

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Cell Cycle and Apoptosis
R. C. Gupta M.D. (Biochemistry) Jaipur,
India
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Cell cycle
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G1
M
G2
S
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Hunt
Hartwell
Nurse
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Cyclin B- CDK1
Cyclin A- CDK 1 2
Cyclin E- CDK2
Cyclin D- CDK 4 6
G1
M
S
G2
Cyclin-cdk complexes regulate the cell cycle
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Checkpoints
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The checkpoints verify that all the events
required for progression to the next phase have
occurred
The cell cycle cannot go to the next phase until
checkpoint requirements have been met
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G2/M checkpoint
G1/S checkpoint
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G1/S checkpoint
G1/S checkpoint monitors whether all the
requirements for DNA synthesis have been met
G1/S transition is the rate-limiting step in
cell cycle
This is also known as the restriction point
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Normally, cyclin D level rises in G1 phase which
activates CDK4 and CDK6
This pushes the cell cycle into S phase
In G1 arrest, CDK4 and CDK6 remain inactive
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G1 arrest gives more time to DNA repair systems
to repair the damage
If the damage is repaired, the cell cycle is
allowed to proceed to the S phase
If the damage cannot be repaired, the cell is
pushed into apoptosis
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G2/M checkpoint
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Apoptosis
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Necrosis
Apoptosis
Unnatural cell death
Natural cell death
Cell is programmed to die
Acute injury results in cell death
Results in disease, if excessive
Generally confers some advantage
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Caspase
Glu?Ala?Val?Asp?Leu?Arg?Phe?Ser
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Extrinsic (extracellular) pathway
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Intrinsic (mitochondrial) pathway
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SMACs
Procaspase
T
T
IAP
Caspase
Release of SMACs inhibits IAP and allows
activation of procaspases
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Release of cytochrome c leads to activation of
procaspase 9
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Morphology of apoptotic cells
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Thank you