29_Cell Cycle II Flashcards Preview

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Flashcards in 29_Cell Cycle II Deck (15)
1

Where does Wee-1 phosphorylate cdc2 at?

Tyr-15
(inhibitory effect)

2

What protein phosphorylates cdc2 at Thr-161?

CAK (cyclin activating kinase)

3

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

cdc24
Result: activation of the MPF and entry into mitosis

4

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

Wee 1: -
cdc25: +

5

What do wee 1 mutants look like? Why?

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

6

Why can't cdc25 mutants enter mitosis?

They cannot remove inhibitory phosphate from Tyr-15.

7

How does proteolysis regulate CDK activity?

proteolysis of cyclins can be both an accelerator and brake

8

How does subcellular localization of cyclins regulate CDKs?

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

9

Which cyclin's levels oscillate the least?

Cyclin D

10

What does pRB do in its activated state?

represses genes required for S phase

11

During G1, what is E2F bound to?

pRB (and the gene promoter)

12

What effect does CDK activation have on pRB?

pRB is phosphorylated => becomes inactive

E2F is released, and transcription is activated

13

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

CDIs (cyclin-dependent kinase inhibitors)

14

Which CDI family are binary inhibitors? Ternary?

Binary: INK4
Ternary: CIP/KIP

15

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

INK4: p16
CIP/KIP: p21