Cell Cycle & Cancer- Week 1 Flashcards
What are the cell’s options in G1 phase?
1) Senescence and differentiation (Gnot)
2) Apoptosis
3) Proliferation via cell cycle
What is purpose of S phase?
synthesis of chromatin (DNA and Histones)
What occurs during G2 phase?
centrosome duplicates- (centrosome=area in which the mitotic spindles originate)
What is centrosome?
are in which the mitotic spindles originate
In what order do cyclin molecules work in the cell cycle?
D–>E–>A–>B
In what order to CDK’s work in cell cycle?
4, 2, 1
What is purpose of CDK’s in cell cycle?
phosphorylate proteins to regulate cell cycle
During cell cycle, the content of part of the Cyclin+CDK subunit changes and the other doesn’t. Which one changes?
Cyclin “cycles” during the cell cycle
What amino acids do cycline-dependent protein kinase heterodimers phosphorylate?
Serine, Threonine, tyrosine
What do factors are involved at the onset of cell cycle and what do they do?
p27 (a CDK inhibitor) decreases and stays low
cyclin-D production increases and remains high
Explain the cascade of events at checkpoint 1 of early G1 phase
1-Growth factors bind to cell membrane and initiate a response to the myc response factor in nucleus
2- This promotes the transcription of cyclin-D
3- cyclin-D RNA leaves nucleus and is translated into cyclin-D protein
4-cyclin D binds to CDK-4
5- cyclin-D/CDK-4 phosphorylates retinoblastoma (Rb)
6- phosphorylated Rb releases E2F (a transcription factor)
7- E2F activates genes for cyclin-E and cyclin-A
Explain the cascade of events at checkpoint 2 at end of G1 start of S phases
1-Cyclin-E leaves the nucleus and is translated to protein
2- Cyclin E binds CDK2
3- CyclinE/CDK2 breach restriction checkpoint via phosphorylation of target proteins to initiate S phase
Purpose of p53
p53 (known as the sentinel of the genome) - inhibits cell cycle at the G1/S
*Note: p53 is mutated in 1/2 of cancers
How does p53 accomplish its purpose?
It inhibits the cell cycle at G1/S by inducing p21 which binds to and inhibits CDK2
