Regulation of Cell Cycle RR

Question 1

What are the 3 major check points in the cell cycle? What is the cell checking for at each point?

Answer 1

Enter S- Does the cell have the correct external signals and internal cues to divide
Enter M- Is there any DNA damage that occurred during replication
Exit M- Are all the chromosomes aligned properly and is there tension on all kenetichores

Question 2

Where do terminally differentiated cells usually reside in the cell cycle?

Answer 2

G1 or G0

Question 3

What is a CDK? What is a Cyclin? How are they related?

Answer 3

CDK is a cyclin dependent kinase. The kinase can only function with its proper regulatory cyclin subunit attached?

Question 4

Describe how the levels of CDKs and Cyclins change throughout the cell cycle? (In general terms, not a specific cdk/cyclin)

Answer 4

CDKs are usually held at a constant level and cyclins levels increase or decrease dependent on the cell cycle stage

Question 5

Describe the steps required to activate a CDK

Answer 5

1) bind specific cylcin to cdk
2) Kinase adds inhibitory phosphate to cdk
3) Kinase adds activating phosphate to cdk
4) Phosphatase removes inhibitory phosphate

Question 6

For mitotic Cdk waht is the name of the inhibitory kinase, activating kinase, and activating phophatase?

Answer 6

Inhibitory kinase- wee1
activating kinase- Cak
Activating Phosphatase - Cdc 25

Question 7

If Wee 1 is defective what is the result in the dividing cell?

Answer 7

premature activation of mitotic Cdk will cause the cell to divide prematurely and result in small daughter cells.

Question 8

Describe how positive feedback plays a role in cdk activation?

Answer 8

Active Cdk cause further activation of the activating phosphatase and thus more active cdk

Question 9

Describe the process of cdk inactivation?

Answer 9

The cyclin subunit is ubiquitylated by an E3 ubiquitin Ligase and is degraded by the proteosome. The activated phosphate is then removed from the cdk

Question 10

Describe the function of APC?

Answer 10

APC (anaphase promoting complex) triggers anaphase both by turning off cdk activity and also by promoting chromosome separation by ubuiquitylating Secruin (which gets destroyed) which frees up Seperase which cleaves cohesins.

Question 11

Describe the activation and downstream functions of p53?

Answer 11

DNA damage triggers kinases that activate p53 (Phosphorylation). p53 binds to regulatory region of p21 gene and upregulates transcription. The p21 protein is a cdk inhibitor

Question 12

What are the BRCA1, BRCA2, and PARP genes? How do they function normally?

Answer 12

BRCA 1 and 2 are DNA repair genes that repair double strand breaks. PARP gene is invovled in single strand break repair

Question 13

What is cisplatin?

Answer 13

Cisplatin is a drug used to treat cancers which are deficient in DNA repair. It causes increased DNA damage which these cancer cells are especially vulnerable to.

Question 14

In a very general sense what effects do all growth factors have on cells?

Answer 14

Increase protein synthesis and decreased protein metabolism. Both lead to cel growth.

Question 15

What signaling pathway do many growth factors work through?

Answer 15

Ras and MAP kinase

Question 16

What is the retinoblastoma protein? How are Cdk involved with it?

Answer 16

The Rb protein when in its active form is a transcription inhibitor. Activated G1 and G1/S cdk phosphorylate Rb which renders it inactive. Transcription is then free to proceed.