10-23: Cell cycle control and cell division

Question 1

Cell cycle control

Answer 1

• DNA replication to 2 identical daughter cells
• 3 major checkpoints
• many of the genes (proteins) involved in cell cycle regulation are critical determinants of cancer progression

Question 2

Interphase

Answer 2

G1: growth and metabolic
S: replication of DNA
G2: growth and prep

Question 3

Mitosis

Answer 3

P: condensed
M: center
A: segregate
T: decondensed

Question 4

Cytokinesis

Answer 4

Cell splits (two identical daughter cells)

Question 5

Resting Phase

Answer 5

G0

Question 6

G1/S Checkpoint

Answer 6

Check for:
Nutrients
Growth factors
DNA damage

Question 7

G2/M Checkpoint

Answer 7

Check for:
cell size
DNA replication

Question 8

Metaphase to anaphase checkpoint

Answer 8

Check for chromosome spindle attachment

Question 9

Cell cycle checkpoint control system

Answer 9

1. Dependant on cyclically activated cyclin dependant protein kinases (Cdks)
2. dependant on cyclical proteolytic events
3. dependant on transcriptional regulation

Question 10

Cell cycle checkpoint control system

Answer 10

1. Initiates/ends events
2. proper order and fidelity
3. Intracellular and extracellular dependant
4. Arrests the cycle (fails to complete a process or unfavorable conditions)

Question 11

cyclins and cyclin dependant protein kinases

Answer 11

1. Cdk binds to cyclin
2. phosphorylation
3. active cyclin Cdk complex

Question 12

Cyclin D

Answer 12

Cyclin D

Question 13

Cyclin E

Answer 13

G1/S cyclin

Question 14

Cyclin A

Answer 14

S cyclin

Question 15

Cyclin B

Answer 15

M cyclin

Question 16

The concentrations of cyclins _____________ while Cdk ________________.

Answer 16

The concentrations of cyclins CHANGE while Cdk DO NOT CHANGE.

Question 17

Anaphase-promoting complex (cytosome)

Answer 17

APC/C: initiates the metaphase to anaphase transition

Question 18

What happens to expose the active site on CDK?

Answer 18

1. Cyclin binds to cdk
2. Opens up the T loop (Partial active)
3. T loop is phosphorylated, fully active (fully active)

Question 19

The activity of cyclin-cdk is further regulated by

Answer 19

WEE 1 kinase= phos Cdk at different site= INACTIVE
Cdc25 phosphatase= removes the wee phos= ACTIVE

Question 20

Proteolysis

Answer 20

protein degradation

Question 21

What family of proteins is the anaphase-promoting complex?

Answer 21

ubiquitin ligase

Question 22

Function of APC/C

Answer 22

trigger metaphase -> anaphase by tagging specific proteins for degradation

Question 23

What does APC/C catalyze?

Answer 23

ubiquitylation and degradation of securin and the S and M cyclins

Question 24

When is APC/C active?

Answer 24

Mid mitosis and remains active in G1

Question 25

Control of cell cycle through APC/C

Answer 25

Cdc 20 activates APC/C -> ubiquitinizes m-cyclin

Question 26

SCF

Answer 26

Skp1, cullins, F-box proteins

Question 27

What family of proteins is SCF?

Answer 27

Ubiquitin ligase

Question 28

Function of SCF

Answer 28

Ubiquitylates Cdk inhibitor (CKI) proteins in LATE G1 (like p27)

Question 29

Control of proteolysis by SCF

Answer 29

1. SCF binds to F box protein = active
2. Ubiquitinizes Cdk inhibitor protein
3. Cdk inhibitor is degraded in proteasome

Question 30

3. Control by transcription

Answer 30

Cyclin gene expression is regulated and specific cyclin genes are turned on

Question 31

G0

Answer 31

• lack of growth factors/nutrients
• term diff: (heart muscles, nerve cells, bone osteocytes)