29_Cell Cycle II Flashcards Preview

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Flashcards in 29_Cell Cycle II Deck (15)
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1
Q

Where does Wee-1 phosphorylate cdc2 at?

A

Tyr-15

inhibitory effect

2
Q

What protein phosphorylates cdc2 at Thr-161?

A

CAK (cyclin activating kinase)

3
Q

What enzyme dephosphorylates cdc2 at Tyr-15? What is the result of this?

A

cdc24

Result: activation of the MPF and entry into mitosis

4
Q

Wee 1 is a (+/-) regulator and cdc25 is a (+/-) regulator of mitotic entry.

A

Wee 1: -

cdc25: +

5
Q

What do wee 1 mutants look like? Why?

A

They are small (wee). Since these cells cannot keep cdc2 in an inactive state, they divide prematurely (G2 is too short).

6
Q

Why can’t cdc25 mutants enter mitosis?

A

They cannot remove inhibitory phosphate from Tyr-15.

7
Q

How does proteolysis regulate CDK activity?

A

proteolysis of cyclins can be both an accelerator and brake

8
Q

How does subcellular localization of cyclins regulate CDKs?

A

accelerates (e.g. translocate to nucleus, and become ‘trapped’ there)

9
Q

Which cyclin’s levels oscillate the least?

A

Cyclin D

10
Q

What does pRB do in its activated state?

A

represses genes required for S phase

11
Q

During G1, what is E2F bound to?

A

pRB (and the gene promoter)

12
Q

What effect does CDK activation have on pRB?

A

pRB is phosphorylated => becomes inactive

E2F is released, and transcription is activated

13
Q

What class of proteins inhibit cyclin/CDK activity in early G1?

A

CDIs (cyclin-dependent kinase inhibitors)

14
Q

Which CDI family are binary inhibitors? Ternary?

A

Binary: INK4
Ternary: CIP/KIP

15
Q

Classify the CDIs p16 and p21 as members of INK4 or CIP/KIP.

A

INK4: p16

CIP/KIP: p21