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Biochem IV > cell cycle > Flashcards

cell cycle Flashcards

1
Q

What three cell-cycle phases make up interphase?

A

G1, S and G2

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2
Q

What happens during S phase?

A

DNA is replicated

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3
Q

What stage are differentiated cells in?

A

G0

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4
Q

What cyclin/CDK complex is present in M phase?

A

A/CDK1 and B/CDK1

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5
Q

What cyclin/CDK complex is present in Mid G1 phase?

A

D/CDK4 and D/CDK6

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6
Q

How are cyclins degraded?

A

ubiquitin dependent proteolysis

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7
Q

Genes that respond quickly to an addition of a growth factor are called?

A

early response genes

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8
Q

What is an important early response gene?

A

c-Fos

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9
Q

What three genes transcribe the delayed response genes?

A

c-Fos, c-Jun and c-Myc

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10
Q

A ligand binding causes what two processes to happen to the receptor?

A

dimerization

autophosphorylation of the receptor

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11
Q

What does Sos promote?

A

exchange of GDP for GTP on Ras

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12
Q

What is another name for ERK?

A

MAP kinase

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13
Q

Which kinase of the MAP kinase pathway can enter the nucleus?

A

MAP Kinase

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14
Q

The activation of MAP kinase stimulates txn of what gene?

A

c-Fos

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15
Q

What process leads to progression through the restriction point?

A

increasing c-Fos txn

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16
Q

Which cyclins and CDKs are part of the delayed-response genes?

A

mid G1 and late G1

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17
Q

The retinoblastoma protein is phosphorylated by what cyclin/CDK?

A

cyclin D and CDK 4/6

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18
Q

E2F proteins are proteins of what response?

A

delayed response

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19
Q

E2F proteins activate genes required for what?

A

DNA replication

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20
Q

What cyclins and CDK are activated by E2F?

A

cyclins E and D

CDK2

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21
Q

What is the role of E2F proteins when bound to Rb?

A

repressors of txn

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22
Q

What two complexes does Rb bind that inhibit gene txn?

A

HDAC and methylase complexes

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23
Q

What causes dissociation of Rb from E2F?

A

phosphorylation by cyclin D and CDK 4/6

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24
Q

What product of E2F activation can also activate Rb?

A

E-CDK2

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25
Q

What type of proteins inhibits cyclin D association with CDK4/6? What effect does this have?

A

INK4 proteins

inhibits cell growth

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26
Q

What protein is a member of the INK4 protein class?

A

p16

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27
Q

What is the best understood inhibitor of A-CDK2?

A

p27-KIP1

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28
Q

What phosphorylates p27-KIP1?

A

late G1 cyclins

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29
Q

What does phosphorylation of p27-KIP1 entail?

A

polyubiquitination

subsequent activation A-CDK2

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30
Q

What components of replication does CDK-2 phosphorylate?

A

origin of replication components

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31
Q

What is the most important driver of the events leading up to mitosis?

A

CDK1

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32
Q

How is CDK1 activated?

A

de-phosphorylation

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33
Q

What is the function of cohesin?

A

to hold sister chromatids together at the centromere

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34
Q

What complex degrades cohesion?

A

anapahse promoting complex

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35
Q

What complex polyubiquitinates cyclin A and B?

A

anaphase promoting complex

36
Q

What checkpoint does ATM regulate?

A

G2/M

37
Q

What is the function of ATM?

A

to detect if DNA synthesis is still in process

38
Q

What needs to happen to CDK1 for the cell to enter mitosis?

A

dephosphorylation

39
Q

Ultimately, what does ATM prevent?

A

inhibition of CDK1 dephosphorylation

40
Q

ATM is always active as long as what are present?

A

replication forks

41
Q

What event activates ATM?

A

double stranded DNA breaks

42
Q

What activates ATR?

A

DNA damage caused by UV radiation

43
Q

Are CDK1 and CDK2 active in a phosphorylated or dephosphorylated state?

A

dephosphorylated

44
Q

What effect do ATR/ATM have on CDK1 and CDK2 phosphorylation states?

A

inhibit their dephosphorylation and subsequent activation

45
Q

What does ATR/ATM activation do to p53?

A

Phosphorylates it

46
Q

What does phosphorylation of p53 result in?

A

stabilization and increase in its levels

47
Q

What does p53 do to p21-CIP1?

A

activates it

48
Q

What is the function of p21-CIP1?

A

inhibits the action of cyclin/CDK1 and cyclin/CDK2

49
Q

Ataxia-telangiectasia patients have a mutated copy of what protein?

A

ATM

50
Q

What type of DNA damage are patients with ataxia-telangiectasia?

A

double-stranded DNA breaks

51
Q

Where does chromosome condensation occur in the early stages of apoptosis?

A

around the periphery of the nucleus

52
Q

What happens to cell size during apoptosis? What is this called?

A

shrinks

cytoplasmic condensation

53
Q

What is the intrinsic pathway of apoptosis?

A

activation of p53

54
Q

What two cellular ligands are implicated in the external pathway of apoptosis?

A

Tumor necrosis factor (TNF)

Fas ligand

55
Q

What produces TNF?

A

macrophages

56
Q

What two cell types produce Fas ligand?

A

NK cells and T-lymphocytes

57
Q

What enzymatic activity do caspases possess?

A

cysteine aspartate protease activity

58
Q

p53 activates apoptosis through which three proteins?

A

PUMA, BID and BAX

59
Q

What is the function of BAX? What does this release?

A

to form a channel in the outer mitochondrial membrane

cytochrome c

60
Q

What protein inhibits BAX? What proteins activate BAX?

A

bcl-2 = inhibit

PUMA and BID = activate

61
Q

Upon entry into the cytosol, what does cytochrome c bind to?

A

Apaf-1

62
Q

What does binding of cytochrome C do to apaf-1?

A

induces its oligomerization

63
Q

Which caspases are activated by Apaf-1?

A

caspase-9 and caspase-3

64
Q

What is the role of caspase-9? What is the role of caspase-3?

A

caspase-9 = initiator

caspase-3 = executioner

65
Q

What is the function of Sos?

A

to promote exchange of GDP for GTP on Ras

66
Q

What does increasing the transcription of c-Fos do?

A

pushes the cell through the restriction point

67
Q

INK4 proteins function to do what?

A

inhibit the association of cyclin D with CDK 4 and 6

68
Q

What is the function of cohesion? What promotes the dissolution of cohesin?

A

hold sister chromatids together

anaphase promoting complex

69
Q

The anaphase promoting complex polyubiquitinates which cyclins?

A

A and B

70
Q

What does ATM detect?

A

replication forks

71
Q

What is the purpose of ATM?

A

to prevent M phase before G2 phase is complete

72
Q

Ataxia telangiectasia is caused by mutations to what protein?

A

ATM

73
Q

What cell produces tumor necrosis factor?

A

macrophages

74
Q

What cell produces Fas ligand?

A

natural killer cells

75
Q

What is the early response gene?

A

c-Fos

76
Q

What two proteins join Fos to transcribe the delayed response genes?

A

Jun and Myc

77
Q

What are the delayed response genes?

A

Mid G1 and Late G1 cyclins and CDKs

78
Q

ERK stimulates the txn of what gene?

A

Fos

79
Q

What protein phosphatase is activated at the end of DNA replication?

A

Cdc25c

80
Q

The anaphase promoting complex leads to the destruction of what cyclins?

A

cyclin A and cyclin B

81
Q

What does ATM recognize?

A

replication forks

82
Q

What protein component does ATM inhibit?

A

Cdc25C

83
Q

When ATM/ATR sense DNA damage, what protein do they phosphorylate?

A

p53

84
Q

What protein does p53 upregulate?

A

p21-CIP1

85
Q

What CDKs does p21-CIP1 inhibit?

A

CDK1 and CDK2

86
Q

Patients with ataxia-telangiectasia posses a mutated version of what protein?

A

ATM

87
Q

MAP kinase increases the txn of what DNA binding protein?

A

c-Fos

Biochem IV (6 decks)

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