Regulation of the Cell Cycle Lecture 4 Flashcards
All animal growth is based on _____ ____ or an increase in ____ _____ activity.
- Cell proliferation
- cell cycle
How is cell growth initiated?
By the binding of an extracellular ligand, or growth factor, to a membrane receptor and the activation of kinases that increase gene expression
What is each phase of the cell cycle? Give a brief definition.
- M Phase: Cell division
- G1 Phase: RNA and protein synthesis and major regulatory events
- G0: Resting cells
- S: DNA replication and synthesis
- G2: RNA and protein synthesis, mitotic spindle assembly
What regulates progression through the cell cycle? What mediates these?
- Biochemical reactions, or checkpoints
- Checkpoints are mediated by kinases
Kinases that function as cell cycle checkpoints are composed of what two proteins? Which is the regulatory and which is the catalytic component?
- Cyclin Dependent Kinase (CDK) (Catalytic)
2. Cyclin (Regulatory)
True or False: CDKs without cyclin are unable to function as a kinase and have no catalytic activity.
True
How are cyclin:CDK complexes regulated?
-The genes that encode cyclins are only expressed during specific phases of the cell cycle, and cyclins rapidly degrade after completing their function
What do cyclin:CKD complexes do?
They phosphorylate protein substates in specific phases of the cell cycle, changing the proteins conformation and facilitating progression through the cell cycle. This can increase or decrease, or activate or inhibit, the function of a protein.
Cyclin D is an example of a ____ _____, so proteins encoded by Cyclin D perform similar functions in the body
Gene Family
What doe CyclinD/CDK4/6 and CylinE/CDK2 kinases do?
Phosphorylate and inactivate the retinoblastoma protein (Rb), which must occur for the cell cycle to continue
Rb is active when it is or is not phosphorylated? What does it do when it is active?
- Is not phosphorylated
- Blocks progression of the cell cycle. It is the original tumor suppressor gene.
How does Rb (retinoblastoma protein) control cell cycle progression?
It binds to E2F. E2F is a transcription factor that binds to DNA at the E2 DNA recognition site, which is in promotor regions of genes that encode proteins that function in G1/S phase cell cycle progression and DNA synthesis in the S phase.
True or False: E2F is active when bound to Rb.
False, it is active when unbound from Rb
Unphosphorylated Rb is (active/inactive) and in a complex with _____, which is (activated/inactivated). This occurs during what cell cycle phases?
- Active
- E2F
- Inactivated
- G0 and early/mid G1
During Mid/Late G1, cyclin D gene is expressed. What does this do?
-Cyclin D forms an active kinase complex with CDK4/6, which then phosphorylates Rb and inactivates it, causing E2F to be released. Free E2F activates the transcription of genes encoding proteins needed in late G1 and S phase.
