Cell Cycle 2

Question 1

Which cyclin is active during G1?

S-phase?

G2?

Mitosis?

Answer 1

G1: Cyclin D + CDK 4/6, also cyclin E + CDK2

S-phase: Cyclin E + CDK2

G2: Cyclin A + CDK1

Mitosis: Cyclin B + CKD1

Question 2

What is the restriction point? Where is it located?

Answer 2

The point in the cell cycle when the cell is committed to S-phase. Located at end of G1.

Question 3

Myc

• Is this an early gene or delayed gene?
• What does myc do?
• Why is mutation involving myc often associated with cancer?

Answer 3

• Early
• Transcription factor that promotes transcription of genes needed to progress through G1, specifically cyclin D
• Myc has strong growth promoting activity. When it is translocated such that it is moved after the promoter for an antibody gene, it is transcribed a lot and induces a lot of rapid cell division

Question 4

What kind of gene is myc?

What kind of gene is pRB?

Answer 4

Oncogene

Tumor suppressor

Question 5

Human Papilloma Virus

• What are its targets?
• How does it target each of these proteins?

Answer 5

• p53 and pRb
• E6 enzyme is Ubiquitin E3 ligase that targets p53
• E7 enzyme binds to pRb and inhibits function