Tumour Pathology 4 Flashcards
What is the cell cycle?
The time between mitotic divisions
4 phases of the cell cycle?
- Mitosis (M)
- Synthesis of DNA synthesis components (G1)
- DNA synthesis (S)
- Prep for mitosis (G2)
What external factors are involved in cell cycle control?
- Hormones
- Growth Factors
- Cytokines
- stroma
What intrinsic factors help control the cell cycle?
Critical checkpoints such as teh restriction point (R) just before G1.
Crossing these checkpoints requires external stimuli to continue.
What phases of teh cell cycle are referred to as interphase?
G1
S
G2
Describe some cell cycle checkpoints:
- IF teh cell size is inadequate it stops at G1 or G2
- If nutrient supply inadequate, stops at G1
- DNA not replicated, stops at S
- Chromosome mis-alignment, M arrest
What makes up the checkpoints?
Enzymes.
Specifically a catalytic sub-unit activated by a regulatory sub-unit
What are the catalytic sub-units in cell cycle checkpoints?
Cyclin-dependent kinases (CDKs)
What are the regulatory sub-units in cell cycle checkpoints called?
Cyclins
What do call teh active enzyme complex in a cell cycle checkpoint?
A CDK/cyclin complex
How do CDK/Cyclin complexes regulate the cell cycle?
CDK/cyclin complex phosphorylates a substrate
-> substrate is either activated or inactivated
-> substrate regulates the next cell cycle
What two things regulates CDK activity?
- Cyclin production/destruction
- CDK inhibitors (CKIs)
What does the retinoblastoma gene code for?
A protein called pRb
What does pRb do?
When activated it Inactivates E2F transcription factor
(applies a brake to the cell cycle)
How is E2F normally activated?
By Cyclin D/CDK complex phosphorylating (inactivating) pRb
