Cell Cycle Regulation; Intro to Cancer
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In which phase is the cell not dividing.
The G0 phase
G0 phase is viewed as either an extended G1 phase, where the cell is neither dividing nor preparing to divide, or a distinct quiescent stage that occurs outside of the cell cycle.
Under are regulated at which phase(s)?
3 major check points: in G1, G2, M phases
Which phase is the most important and why?
- The G1 phase (Called the Restriction Point). If a cell gets the signal to pass the Restriction Point; it usually finishes the cell cycle.
- This cycle is the most important because it ensures that the cell has the right amound of DNA. Not true for any other stop points.
What is the job of the Protein Kinases.
Kinases provides the cell cycle signals. They add phosphate groups to other proteins; phosphorylates them and change their conformation and activity.
What types of Kinases regulate cell cycle?
CDK's (cell division kinases)
How can CDK become active?
- ACTIVE when bound to a cyclin protein
- Each cdk is active ONLY when the level of ITS CYCLIN is high
- INACTIVE alone
- Each cdk binds to a Different cyclin
Which cyclin-cdk complex is involved in G2 and tells the cell to begin Mitosis
- Mitosis Promoting Factor (MPF) - a cycin cdk complex (2 protein)
- Acts at G2 checkpoint
- Triggers entry into mitosis
- Binds with cdck-2
Phosphorylation of nuclear lamin proteins by MPF causes:
nuclear envelope fragmentation in prometaphase
What is the function of nuclear lamins?
The nuclear lamins provides support for the nuclear envelope.
What is the job of MPF in the metaphase of mitosis?
- MPF activity induces proteases that degrade (break down) proteins holding sisters chromatids together.
- This starts anaphase
How does MPF become inactive?
- MPF activity induces proteases that degrade its cyclin.
- This inactivates MPF and ends mitosis.
What signal cells to dividle?
growth factors (ex. PDGF) can trigger division
How do cell in wounds know when to begin reproducing to begin the healing process.
Platelets (blood cells) go to wound site and release PDGF (Platelet Derived Growth Factor)
PDGF binds to receptor tyrosine kinase on cells near wound.
PDGF signaling pathwat stimulates synthesis of G1 cyclin
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