Tumour Pathology 4 Flashcards
How does cell division occur?
Normal cell cycle and mitosis
What do checkpoints do?
- monitor and regulate process
- prevent progression at specific points
Examples of checkpoint and their function?
the G1 checkpoint at the G1/S transition
-Once the cell passes the G1 checkpoint and enters S phase, it becomes irreversibly committed to division.
What is the cell cycle?
The ordered sequence of events that occur in a cell in prep for cell division.
four-stage process in which the cell increases in size (G1), copies its DNA (S), prepares to divide/mitosis (G2, ), and divides (mitosis, or M, stage).
What external factors are involved in cell cycle control?
- hormones
- growth factors
- cytokines
What phases of the cell cycle are referred to as Interphase?
G1
S
G2
Describe some cell cycle checkpoints
If cell size is inadequate, it stops at G1 or G2
- if nutrient supply is inadequate it stops at G1
- DNA is not replicated, it stops at S
- Chromosome mis-alignment, M arrest
What are the checkpoint activators?
- Enzymes
- A catalytic sub-unit activated by a regulatory sub-unit cyclin
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 the active enzyme complex in a cell cycle checkpoint?
A CDK/cyclin complex
How do CDK/Cyclin complexes regulate the cell cycle?
Active CDK/cyclin complex phosphorylates target proteins
- > results in activation/inactivation of target proteins
- > substrate regulate events in the next cell cycle phase
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 pRb is phosphorylated it becomes inactive and loses affinity/activates for E2F transcription factor
(applies a brake to the cell cycle)
