CyclinD

Question 1

Which Cyclin forms active complexes with CDK4 and CDK6 during the G1 phase?

Answer 1

Cyclin D

Question 2

What is the function of Cyclin D-CDK4/6 complexes in the G1 phase?

Answer 2

They phosphorylate the retinoblastoma protein (Rb).

Question 3

What effect does hypophosphorylated Rb have on E2F transcription factors?

Answer 3

It binds to them, preventing the initiation of gene transcription required for S phase entry.

Question 4

What happens to Rb when phosphorylated by Cyclin D-CDK4/6?

Answer 4

It becomes inactivated, releasing E2F.

Question 5

What is the role of E2F after its release from Rb?

Answer 5

It promotes the transcription of genes necessary for DNA replication.

Question 6

What critical checkpoint must a cell pass to commit to entering the S phase?

Answer 6

The restriction point (R-Point).

Question 7

Which complexes are crucial for a cell to pass the restriction point in late G1?

Answer 7

Cyclin D-CDK4/6 complexes.

Question 8

What phase does the cell enter after passing the restriction point?

Answer 8

The S phase.

Question 9

How does phosphorylation affect the retinoblastoma protein (Rb)?

Answer 9

It inactivates Rb, allowing the cell cycle to progress.

Question 10

What is the consequence of E2F being released from Rb in the cell cycle?

Answer 10

It initiates the transcription of genes required for DNA replication.

Question 11

What determines if a cell commits to DNA replication regardless of external signals?

Answer 11

Passing the restriction point (R-Point) in late G1.

Question 12

What prevents E2F from initiating S phase gene transcription when bound to it?

Answer 12

Hypophosphorylated retinoblastoma protein (Rb).

Question 13

What is the main function of Cyclin D in cell cycle regulation?

Answer 13

To partner with CDK4 and CDK6 to phosphorylate Rb, facilitating the G1/S transition.

Question 14

What is the role of Cyclin D-CDK4/6 complexes in the G1 phase?

Answer 14

They phosphorylate the retinoblastoma protein (Rb), promoting the G1/S transition.

Question 15

What happens to retinoblastoma protein (Rb) when phosphorylated by Cyclin D-CDK4/6?

Answer 15

It becomes inactivated, releasing E2F transcription factors.

Question 16

What is the consequence of E2F release during the G1 phase?

Answer 16

E2F promotes the transcription of genes required for S phase entry.

Question 17

How does Rb protein regulate the G1/S transition before phosphorylation?

Answer 17

It binds to E2F, preventing transcription of S phase genes.

Question 18

What is the Restriction Point (R-Point) in the cell cycle?

Answer 18

A checkpoint in late G1 where the cell commits to entering the S phase.

Question 19

What is the significance of passing the Restriction Point in the G1 phase?

Answer 19

The cell commits to DNA replication, regardless of external signals.

Question 20

How do Cyclin D-CDK4/6 complexes influence the Restriction Point?

Answer 20

Their activity is crucial for passing the Restriction Point.

Question 21

What does hypophosphorylated Rb do?

Answer 21

Binds to E2F, inhibiting the transcription of genes required for S phase.

Question 22

What marks the commitment to the S phase?

Answer 22

The cell passing the Restriction Point.

Question 23

What phase of the cell cycle is regulated by Cyclin D-CDK4/6 activity?

Answer 23

The G1 phase.

Question 24

Which transcription factors are released upon Rb phosphorylation?

Answer 24

E2F transcription factors.

Question 25

Why is Cyclin D important in the cell cycle?

Answer 25

It partners with CDK4/6 to regulate the G1/S transition.

Question 26

What triggers the inactivation of Rb protein?

Answer 26

Phosphorylation by Cyclin D-CDK4/6 complexes.

Question 27

What is the clinical significance of dysregulation of Cyclin D in oncogenesis?

Answer 27

It leads to uncontrolled cell proliferation due to aberrant activation of CDK4/6, observed in various cancers.

Question 28

In which cancer is Cyclin D1 overexpression particularly associated?

Answer 28

Mantle cell lymphoma.

Question 29

What role does Cyclin D1 play in cancer development?

Answer 29

It acts as an oncogene, promoting tumorigenesis by overriding normal cell cycle controls.

Question 30

How is Cyclin D1 overexpression linked to breast cancer?

Answer 30

It contributes to tumorigenesis by driving cell proliferation.

Question 31

What is the therapeutic approach targeting Cyclin D-CDK4/6 complexes in cancer treatment?

Answer 31

Use of specific inhibitors like palbociclib, ribociclib, and abemaciclib.

Question 32

Which cancers are CDK4/6 inhibitors particularly effective against?

Answer 32

Hormone receptor-positive breast cancer.

Question 33

How do CDK4/6 inhibitors work?

Answer 33

They block the kinase activity of CDK4/6, leading to cell cycle arrest in G1 phase.

Question 34

Name a mechanism by which cancer cells develop resistance to CDK4/6 inhibitors.

Answer 34

Upregulation of Cyclin E-CDK2 activity.

Question 35

What is another mechanism of resistance to CDK4/6 inhibitors?

Answer 35

Loss of Rb function.

Question 36

How does overexpression of CDK6 contribute to resistance to CDK4/6 inhibitors?

Answer 36

It bypasses the inhibition and allows cell cycle progression.

Question 37

Why is Cyclin D1 overexpression a significant marker in esophageal cancer?

Answer 37

It indicates a higher likelihood of aggressive tumor behavior.

Question 38

What is a common outcome of gene amplification involving Cyclin D1 in cancers?

Answer 38

Increased cell cycle progression leading to tumor growth.

Question 39

How does chromosomal translocation involving Cyclin D1 affect cancer development?

Answer 39

It can result in abnormal Cyclin D1 expression, driving oncogenesis.