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Molecular cell bio > F lec 18 > Flashcards

F lec 18 Flashcards

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Biology 101 flashcards
1
Q

in _____ of the cell cycle a pre-replication complex (preRC) forms at origins of replication

A

G1

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2
Q

at S phase, the _________’s are sites where the 2 kinases DDK and CDK2 phosphorylate substrates to promote DNA replication by DNA polymerase

A

preRC

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3
Q

enzyme in S phase that phosphorylates MCM helicase

A

DDK

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4
Q

enzyme in S phase that phosphorylates initiator proteins

A

CDK2-cycA

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5
Q

CDK2-cyclin A phosphorylates ________________ ______________ at the preRC in S phase

A

initiator proteins

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6
Q

DDK phosphorylates ______ ___________________ at the preRC in S phase

A

MCM Helicase

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7
Q

in higher eukaryotes, the G1 cyclin is _________ / ____________ and is inhibited by INK4

A

CDK4, cyclin D

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8
Q

in higher eukaryotes, the G1/S cyclin is ___________/ _______________, which is inhibited by p27 and p21

A

CDK2, cyclin E

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9
Q

in higher eukaryotes, the S cyclin is ___________/ ______________ , which is inhibited by p27 and p21

A

CDK2, cyclin A

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10
Q

CDK4- cyclin D is inhibited by ___________

A

INK4

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11
Q

CDK2- cyclin E is inhibited by _________ and _________

A

p27, p21

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12
Q

CDK2- cyclin A is inhibited by ________ and _________

A

p27, p21

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13
Q

after anaphase, APC cdc20 is inactivated and cyclin levels start to ________, which is what leads to _____-_____________

A

rise, S-phase

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14
Q

in G1, there is ______ CDK activity

A

low

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15
Q

after anaphase, APC ________ is inactivated

A

cdc20 (once mitotic cyclins are degraded to complete anaphase)

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16
Q

after anaphase, APC _________ becomes active

A

cdh1

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17
Q

APC cdc20 and APC cdh1 are __________________ regulated by phosphorylation (CDK phosphorylation is decreasing due to inactivation of CDKs upon completion of anaphase)

A

oppositely

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18
Q

APC cdc20 is only active when ________________

A

phosphorylated

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19
Q

APC cdh1 is only active when ___________________

A

dephosphorylated (there is no phosphorylation)

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20
Q

APC ___________ is activated in mitosis and then inactivated after it degrades cyclins upon the completion of anaphase

A

cdc20

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21
Q

APC __________ is activated when there is low CDK activity - and has the job of maintaining low cyclin levels (keeping them low)

A

cdh1

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22
Q

______ is defined as the point in the cell cycle with little to no CDK activity

A

G1

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23
Q

in G1 of the cell cycle there are 3 things that keep CDK activity low:

A

cdh1 becomes active, cyclins are at low transcription levels, CDK inhibitors present (mentioned previously INK4, p21, p27 and there are many more undiscussed)

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24
Q

cdh1 and CDK inhibitors, along with the low transcriptional levels of cyclins in G1, help keep CDK activity low in G1 which is what allows for ______________ __________________

A

preRC assembly

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25
Q

APC cdh1 ________________ _____________ to degrade them

A

ubiquitinates cyclins (A and B)

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26
Q

______ and ______ bind and inhibit CDK2/ cyclin A and CDK2/ cyclin E

A

p21, p27

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27
Q

_____________ binds and inhibits CDK4/ cyclin D

A

INK4

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28
Q

in G1, ________________ transcription is low

A

cyclin

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29
Q

cells that are terminally differentiated (most cells in our body) arrest permanently in a G1-like state referred to as ______

A

G0

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30
Q

in unicellular organisms the main determinant of the rate of cell division is _______________ __________________ for the cell

A

nutrient availability

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31
Q

in multicellular organisms the rate of cell division is largely determined by ____________________ ______________, typically from neighboring cells

A

extracellular signals

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32
Q

in most cells, the decision of when and if to divide is made in _____ of the cell cycle

A

G1

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33
Q

entry into ___-____________ involves sequential activation of G1-CDKs —> G1/S- CDKs —> S-CDKs

A

S-phase

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34
Q

cell growth is roughly equated with ___________ ______________

A

protein synthesis

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35
Q

rate of cell division must be coupled to the rate of __________ ______________

A

cell growth

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36
Q

in S. cerevisiae (budding yeast), nutrients entering the cell activate the kinase __________

A

TOR

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37
Q

protein activated by nutrients entering the cell that promotes protein synthesis by promoting ribosome synthesis and ribosome activity, as well as inhibiting 4EBP (discussed earlier in the course)

A

TOR

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38
Q

in _____________ _____________, the growth and protein synthesis generated by the TOR pathway will also signal entry into the S-phase from G1

A

budding yeast

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39
Q

in budding yeast, the G1 cyclin ________ is very unstable (constantly subject to ubiquitin-proteasome degradation)

A

Cln3

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40
Q

in budding yeast, the G1 cyclin Cln3 is very _____________

A

unstable

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41
Q

Cln3 ______________ is inefficient, so accumulation of Cln3 only occurs when translation machinery is highly active

A

translation

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42
Q

Cln3 translation is inefficient, so accumulation of Cln3 only occurs when translation machinery is ____________ _____________

A

highly active

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43
Q

because Cln3 only accumulates when translation is highly active, Cln3 acts as a sensor for ___________ __________ and CDK1-Cln3 activity leads to progression into S-phase

A

growth rate

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44
Q

because Cln3 only accumulates when translation is highly active, Cln3 acts as a sensor for growth rate and ________-_________ activity leads to progression into S-phase

A

CDK1-Cln3

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45
Q

because Cln3 only accumulates when translation is highly active, Cln3 acts as a sensor for growth rate and CDK1-Cln3 activity leads to progression into ____-___________

A

S-phase

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46
Q

under ______ ____________ ______________, yeast cell makes less protein and does not divide

A

low nutrient conditions

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47
Q

under _________ _____________ ________________, TOR is active so there is increased translation and more growth so therefore translation of Cln3 is highly active, so there is higher activity of CDK/Cln3 which triggers entry into S-phase

A

high nutrient conditions

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48
Q

extracellular proteins called ________________ signal the cell to divide

A

mitogens

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49
Q

growth factors and mitogens often bind to the same receptors, which are transmembrane ______________ ______________ _______________

A

receptor tyrosine kinases

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50
Q

extracellular regulators of growth are called ____________ __________________

A

growth factors

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51
Q

extracellular regulators of survival (prevent a cell from performing apoptosis) are called ______________ _______________

A

survival factors

52
Q

the effect of a given extracellular signal depends on the cell ________________ ____

A

receiving it

53
Q

many _______________ are also growth factors

A

mitogens

54
Q

many mitogens such as ____________ and _________ activate the Ras/ MAPK pathway and receptor tyrosine kinase binding causes the receptor to dimerize and trans-phosphorylate - then that receptor can recruit Grb2 (which is an SH2 domain protein recruited to the receptor), then Grb2 binds to Sos (a GEF for Ras) which leads us into a pathway called the Ras/ MAPK pathway

A

PDGF, EGF

55
Q

many mitogens such as PDGF and EGF activate the Ras/ MAPK pathway and receptor tyrosine kinase binding causes the receptor to ______________ and ______________________ - then that receptor can recruit Grb2 (which is an SH2 domain protein recruited to the receptor), then Grb2 binds to Sos (a GEF for Ras) which leads us into a pathway called the Ras/ MAPK pathway

A

dimerize, trans-phosphorylate

56
Q

many mitogens such as PDGF and EGF activate the Ras/ MAPK pathway and receptor tyrosine kinase binding causes the receptor to dimerize and trans-phosphorylate - then that receptor can recruit ___________ (which is an _________ _____________ protein recruited to the receptor), then Grb2 binds to Sos (a GEF for Ras) which leads us into a pathway called the Ras/ MAPK pathway

A

Grb2, SH2 domain

57
Q

many mitogens such as PDGF and EGF activate the Ras/ MAPK pathway and receptor tyrosine kinase binding causes the receptor to dimerize and trans-phosphorylate - then that receptor can recruit Grb2 (which is an SH2 domain protein recruited to the receptor), then Grb2 binds to _________ (a ______ for Ras) which leads us into a pathway called the Ras/ MAPK pathway

A

Sos, GEF

58
Q

many mitogens such as PDGF and EGF activate the Ras/ MAPK pathway and receptor tyrosine kinase binding causes the receptor to dimerize and trans-phosphorylate - then that receptor can recruit Grb2 (which is an SH2 domain protein recruited to the receptor), then Grb2 binds to Sos (a GEF for ________) which leads us into a pathway called the Ras/ MAPK pathway

A

Ras (activates Ras)

59
Q

Once Ras becomes bound to GTP after being activated by the GEF Sos, Ras-GTP binds to _______ and activates it, which then phosphorylates MEK to activate it, which then phosphorylates MAPK, allowing MAPK to enter the nucleus

A

Raf

60
Q

Once Ras becomes bound to GTP after being activated by the GEF Sos, Ras-GTP binds to Raf and activates it, which then ______________________ ________ to activate it, which then phosphorylates MAPK, allowing MAPK to enter the nucleus

A

phosphorylates MEK

61
Q

Once Ras becomes bound to GTP after being activated by the GEF Sos, Ras-GTP binds to Raf and activates it, which then phosphorylates MEK to activate it, which then ________________ ___________, allowing MAPK to enter the nucleus

A

phosphorylates MAPK

62
Q

Once Ras becomes bound to GTP after being activated by the GEF Sos, Ras-GTP binds to Raf and activates it, which then phosphorylates MEK to activate it, which then phosphorylates MAPK, allowing MAPK to enter the ________________

A

nucleus

63
Q

_________ _______________ is the kinase that can phosphorylate transcription factors in the nucleus to activate them

A

MAP kinase

64
Q

once MAPK enters the nucleus, it phosphorylates and activates ________________ _____________ that promote the expression of 2 genes called myc and fos

A

transcription factors

65
Q

once MAPK enters the nucleus, it phosphorylates and activates transcription factors that promote the expression of 2 genes called ________ and _________

A

myc, fos

66
Q

_________ binds to a protein called jun to form the AP1 transcription factor

A

fos

67
Q

fos binds to a protein called _______ to form the _______ transcription factor

A

jun, AP1

68
Q

myc and fos promote _______________ ____ ________________

A

cyclin D transcription

69
Q

_________ represses INK4 transcription and therefore helps activate CDK4 (G1 cyclin)

A

myc

70
Q

myc ________________ ________ ________________ and therefore helps activate CDK4-cyclin D (G1 cyclin)

A

represses INK4 transcription

71
Q

the accumulation of cyclin D (due to myc and fos) and the reduction of INK4 (due to myc) leads to the activation of _________-______________

A

CDK4- cyclin D (first step in the transition from G1 to S)

72
Q

the same RTK that stimulates the Ras/MAPK pathway may also stimulate the ________ pathway

A

TOR

73
Q

ras, raf, jun, myc were all discovered as _____________ __________________ because they are related to cell division

A

viral oncogenes

74
Q

once activated by myc and fos, CDK4-cyclin D binds _______, helping to relieve the inhibition of CDK2-cyclin E

A

p27 (but p27 does not inhibit CDK4 it only inhibits CDK2 so taking it away just frees up CDK2 with no cost to CDK4)

75
Q

after relief of p27 from CDK2 by CDK4, CDK4-cycD and CDK2-cycE phosphorylate ____ to _______________ it, thus activating the protein E2F1

A

Rb, inactivate

76
Q

after relief of p27 from CDK2 by CDK4, CDK4-cycD and CDK2-cycE phosphorylate Rb to inactivate it, thus activating the protein __________, which drives high level expression of cyclin E and other S-phase genes

A

E2F1

77
Q

after relief of p27 from CDK2 by CDK4, CDK4-cycD and CDK2-cycE phosphorylate Rb to inactivate it, thus activating the protein E2F1, which drives high level expression of ___________ and other S-phase genes

A

cyclin E

78
Q

in _____/_____ cyclin E levels are low and all CDK2 cyclin E complexes are inhibited by p27 or p21 binding

A

G0/G1

79
Q

________________ levels increase in response to mitogens

A

cyclin D

80
Q

CDK4-cyclin D binds and sequesters ______, allowing for low level activation of CDK2-cyclin E

A

p27

81
Q

once activated a tiny bit by CDK4 removing p27, CDK2 cycE can now _________________ ______ itself

A

phosphorylate p27

82
Q

once activated a tiny bit by CDK4 removing p27, CDK2 cycE can now phosphorylate p27 itself - then phosphorylated p27 is recognized by ________ __________________ _____________ and targeted for destruction = POSITIVE FEEDBACK because now CDK2 is activating itself further and further by destroying its own inhibitor

A

SCF ubiquitin ligase

83
Q

both CDK4 and CDK2 phosphorylate and a protein called Rb, which binds to and inhibits the E2F transcription factor, so indirectly the activity of G1 CDK4 and G1/S CDK2 activates _________, which is then available to go and promote transcription

A

E2F

84
Q

the ______ gene is famous because it was the first identified tumor suppressor gene

A

Rb

85
Q

Rb is famous because it was the first identified ______________ _________________ ____________

A

tumor suppressor gene

86
Q

for now, Rb is named after the type of cancer it causes when it is absent, called ____________________

A

retinoblastoma

87
Q

Rb is the ________________ of E2F

A

inhibitor

88
Q

gene that promotes the cell cycle

A

oncogene

89
Q

gene inhibiting the cell cycle

A

tumor suppressor gene

90
Q

E2F also has a positive feedback type of activation because once activated by the removal of the Rb inhibitor by CDK4 and CDK2, E2F can serve as its own _______________ ______________ which provides even further activation of E2F and therefore even more transcription of cycE and cycA, cycA being the critical one for transition into S-phase

A

transcription factor

91
Q

E2F also has a positive feedback type of activation because once activated by the removal of the Rb inhibitor by CDK4 and CDK2, E2F can serve as its own transcription factor which provides even further activation of E2F and therefore even more transcription of cycE and cycA, _________ being the critical one for transition into S-phase

A

cycA

92
Q

E2F also has a positive feedback type of activation because once activated by the removal of the Rb inhibitor by CDK4 and CDK2, E2F can serve as its own transcription factor which provides even further activation of E2F and therefore even more transcription of _________ and ____________, cycA being the critical one for transition into S-phase

A

cycE, cycA

93
Q

once activated _________-___ and ___________-____ can both phosphorylate p27 and then trigger its destruction by SCF ubiquitin ligase, further promoting the activation of any CDK2 complexes

A

CDK2-E, CDK2-A

94
Q

once activated, __________ and ____________ phosphorylate and inactivate APC cdh1 –> and cyclin A is thereby stabilized

A

CDK2-A, CDK2-E

95
Q

once activated, CDK2-A and CDK2-E phosphorylate and inactivate ________ __________ –> and cyclin A is thereby stabilized - which therefore allows for progression into S phase

A

APC cdh1

96
Q

once APC cdh1 is inactivated, __________-_______________ promotes S phase by phosphorylating multiple targets

A

CDK2-cyclin A

97
Q

in higher eukaryotes ______________ pathways are activated by the same thing, those pathways being growth and cell division

A

parallel

98
Q

in yeast, there is more of a ______________ relationship by which growth in the TOR pathway leads to an increase in levels of a G1 cyclin that leads to buildup and entry into S phase

A

linear

99
Q

S phase should only occur _____________ in a cycle of cell division

A

once

100
Q

for DNA replication to occur at S phase, we need pre-replication complexes to form at ____________ ____ ________________ - discrete sites throughout the genome at which complexes assemble in G1 and need to be there to bring replication machinery to that site to initiate DNA replication

A

origins of replication

101
Q

when deciding which sequence becomes the origin of replication, the decision is based on a DNA sequence that attracts the _________

A

ORC (origin of replication complex)

102
Q

after binding to a specific DNA sequence, the ORC brings 2 different proteins to the site in ______, which are cdc6 and cdt1

A

G1

103
Q

after binding to a specific DNA sequence, the ORC brings 2 different proteins to the site in G1, which are _________ and ____________

A

cdc6, cdt1

104
Q

__________ is first attracted to the ORC, and then it recruits cdt1 along with MCM helicase

A

cdc6

105
Q

cdc6 is first attracted to the ORC, and then it recruits ___________ along with ________-______________

A

cdt1, MCM-helicase

106
Q

after MCM-helicase is attracted to the ORC, _________ and ___________ are released

A

cdc6, cdt1

107
Q

after MCM-helicase is attracted to the ORC, cdc6 and cdt1 are ____________________

A

released

108
Q

once MCM-helicase is present at the ORC, the preRC is considered to be ___________________ throughout the rest of G1

A

licensed

109
Q

after licensing of the preRC consisting of MCM-helicase and the ORC, the activity of 2 kinases ( ________ and _________) triggers replication at the origins

A

CDK2, DDK1

110
Q

kinase at the preRC that phosphorylates initiator proteins

A

CDK2-cyclin A

111
Q

kinase at the preRC that phosphorylates MCM-helicase

A

DDK1

112
Q

at the completion of DNA replication, the ________ remain attached to the origin of replication sites - and for the rest of the cell cycle after this replication there is no chance that replication can happen again after one cycle

A

ORCs (inhibiting another round of replication until a cell division has occurred completely)

113
Q

method of detecting DNA replication using a analogue of dTTP that is incorporated into the cells during S-phase, then fixing the cells and detecting this special substance with primary and fluorescent secondary antibodies - only gets incorporated during S phase

A

BrdU incorporation (bromodeoxyuridine)

114
Q

preRC assembly is ___________________ after S-phase to ensure that re-replication does not occur

A

inhibited

115
Q

if the preRC were not present after S-phase, then re-replication would result in ________________ , which is frequently a first step in cancer development

A

tetraploidy

116
Q

if the preRC were not present after S-phase, then re-replication would result in tetraploidy, which is frequently a first step in _________________ _________________

A

cancer development

117
Q

type of APC:

A

APC cdc20

118
Q

type of APC:

A

APC cdh1

119
Q

pre-replication complexes only form when there is ________ CDK activity

A

low (therefore forms in G1)

120
Q

in S-phase, CDK2 at peak activity has a role in initiating replication at the preRC, but CDK2 also has other targets, like phosphorylating _________ which leads to its recognition and degradation by SCF ubiquitin ligase

A

cdc6

121
Q

in S-phase, CDK2 at peak activity has a role in initiating replication at the preRC, but CDK2 also has other targets, like phosphorylating cdc6, which leads to its recognition by ________ ________________ _______________, leading to its degradation = low cdc6 activity

A

SCF ubiquitin ligase

122
Q

in S-phase other than initiating replication at the preRC and phosphorylating cdc6 to target it for degradation, CDK2 also phosphorylates the _________ which inhibits these preRC from forming

A

ORC

123
Q

In S-phase, cdt1 is necessary for preRC formation and is inhibited by a protein called ______________ that is present in G2 and mitosis

A

geminin

124
Q

2 things CDK2 does to prevent the formation of new preRC after S-phase (CDK2 preventing re-replication):

A

phosphorylates ORC so it cannot recruit preRC, phosphorylates cdc6 to target it for degradation

125
Q

__________________ is a protein that aids CDK2 and the prevention of re-replication after S-phase by inhibiting cdt1 from bringing MCM-helicase to a new preRC

A

geminin

126
Q

At S phase Cdk2 phosphorylates and activates a number of proteins to promote origin firing.

A

JUST READ IT

127
Q

At anaphase - APC targets geminin and cyclins for destruction. Low Cdk activity allows Cdc6 accumulation and ORC dephosphorylation and activation.

A

JUST READ IT - relieves inhibition of preRC formation in G1

Molecular cell bio (8 decks)

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