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Molecular Cell Biology > Cell Division and Cell Death > Flashcards

Cell Division and Cell Death Flashcards

1
Q

S phase

A

DNA duplication, cell growth

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2
Q

M phase

A

nuclear division (mitosis) + cytoplasmic division (cytokinesis)

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3
Q

mitosis

A

chromosome segregation (microtubule based)

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4
Q

cytokinesis

A

actin based

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5
Q

interphase

A

S phase and the gap phases

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6
Q

transition from metaphase to anaphase

A

abrupt change in the biochemical state of the cell

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7
Q

Genetic dissection of cell-cycle pathways

A

normal vs. budding and the behaviors of temperature sensitive Cdc mutants

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8
Q

biochemical dissection of cell-cycle pathways

A
  • large egg size

- in vitro recapitulation

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9
Q

Common experimental tools for analyzing cell-cycle

A
  1. BrDU (thymidine analog) labeling

2. FACS profile of DNA content

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10
Q

BrdU labeling

A

labels newly synthesized DNA which targets cells in the S phase

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11
Q

FACS profile of DNA content

A

relative # of DNA in the cell tells you what phase, number of cells tells you how long the phase is
- the fluorescent dye labels DNA in cells

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12
Q

cell-cycle control system

A

triggers the major events of the cell cycle

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13
Q

checkpoints

A

assure that cell cycle continues without defects

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14
Q

CDK (cyclin dependent kinase)

A

control components of cell-cycle
activity regulated by cyclins
Cyclins undergo cycles of synthesis and degradation during cell cycle

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15
Q

Four types of cyclins

A
  1. G1/S
  2. S
  3. M
  4. G1
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16
Q

restriction point (first checkpoint) in late G1

A

the cell commits to cell-cycle entry and chromosome duplication

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17
Q

G2/M checkpoint

A

control system triggers early mitotic events that lead to chromosome alignment on the spindle in metaphase

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18
Q

metaphase-to-anaphase transition

A

control system stimulates sister-chromatid separation, leading to the completion of mitosis and cytokinesis

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19
Q

levels of Cdk proteins

A

constantduring cell cycle

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20
Q

levels of cyclins

A

cyclical

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21
Q

G1/S cyclins

A

activate Cdks in late G1; help trigger progression through start resulting in a commitment to cell-cycle entry. levels fall in S phase

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22
Q

S-cyclins

A

bind Cdks soon after progression through Start and help stimulate chromosome duplication. S-cyclin levels remain elevated until mitosis, and these cyclins also contribute to the control of some early mitotic events

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23
Q

M-cyclins

A

activate Cdks that stimulate entry into mitosis at the G2/M checkpoint. Mechanisms that we discuss later destroy M-cyclins in mid-mitosis

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24
Q

G1 cyclins

A

help govern activities of the g1/S cyclins, which control progression through Start in late G1

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25
Q

inhibitory phosphorylation and Cdk inhibitory proteins (CKIs) can

A

suppress Cdk activity

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26
Q

CDK activity is positively regulated by

A

cyclins and CAK (Cdk activating kinase)

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27
Q

CDK activity is negatively regulated by

A

inhibitory phosphorylation and CKI (Cdk inhibitors)

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28
Q

What controls the cyclins and the CKIs?

A

proteolysis

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29
Q

APC

A

anaphase promoting complex (a ubiquitin ligase)

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30
Q

What does APC do?

A

catalyzes ubiquitylation of securin and S/M cyclins

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31
Q

p27 degradation by

A

phosphorylation

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32
Q

metaphase-anaphase transition controlled by

A

protein destruction - proteolysis

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33
Q

p27

A

CKI, controls the cell cycle progression at G1

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34
Q

Cdk-activating kinase (CAK)

A

phosphorylates an activating site in Cdks

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35
Q

Wee1 kinase

A

phosphorylates inhibitory sites in Cdks; primarily involved in suppressing Cdk1 activity before mitosis

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36
Q

Cdc25 phosphatase

A

removes inhibitory phosphates from Cdks; three family members (Cdc25A, B, C) in mammals; primarily involved in controlled Cdk1 actiation at the onset of mitosis

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37
Q

Sic1 (budding yeast)

A

CI, suppresses Cdk1 activity in G1; phosphorylation by Cdk1 at the end of G1 triggers its destruction

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38
Q

p27 (in mammals)

A

CKI, suppresses G1/S-Cdk and S-Cdk activities in G1; helps cells withdraw from cell cycle when they terminally differentiate; phosphorylation by Cdk2 triggers its ubiquitylation by SCF

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39
Q

p21 (mammals)

A

suppresses G1/S-Cdk and S-Cdk activities following DNA damage

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40
Q

p16(mammals)

A

suppresses G1-Cdk activity in G1; frequently inactivated in cancer

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41
Q

APC/C

A

catalyzes ubiquitylation of regulatory proteins involved primarily in exit from mitosis, including securin and S- and M-cyclins; regulated by association with activating subunits

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42
Q

Cdc20

A

APC/C-activating subunit in all cells; triggers initial activation of APC/C at metaphase-to-anaphase transition; stimulated by M-Cdk activity

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43
Q

Cdh1

A

APC/C-activating subunit that maintains APC/C activity after anaphase and throughout G1; inhibited by Cdk activity

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44
Q

SCF

A

catalyzes ubiquitylation of regulatory proteins involved in G1 control, including some CKIs (Sic1 in budding yeast, p27 in mammals); phosphorylation of target protein usually required for this activity

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45
Q

Cell-Cycle control system functions as

A

a network of biochemical switches

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46
Q

gamma tubulin

A

nucleates MT at MTOC

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47
Q

alpha tubulin binds

A

GTP irreversibly (cant hydrolyze)

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48
Q

beta tubulin binds

A

GTP, hydrolyzes

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49
Q

(+) end vs (-) end

A

+ is beta

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50
Q

How many protofilaments make the structure?

A

13

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51
Q

microtubule assembly principle -

A

similar to that of actin

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52
Q

which end is faster assembly

A

(+) end twice as fast

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53
Q

tubulin assembly dependent on

A

temp
low - dimer
high - polymer

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54
Q

Cc

A

critical concentration - below this polymerization does not take place

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55
Q

how to bypass lag phase

A

add nucleus

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56
Q

treadmilling..

A

at Cc+<Cc-

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57
Q

Assembly of protofilaments

A
  1. linear assembly of aB dimers
  2. lateral association into protofilament (stabilization)
  3. assembly at ends
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58
Q

GTP cap of protofilaments

A

Btubulin adds at GTP before being hydrolyzes

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59
Q

catastrophe

A

shrinking stage

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60
Q

rescue

A

elongation stage

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61
Q

dynamic instability is…

A

an intrinsic property of microtubules

62
Q

determinants of dynamic instability

A

[tubulin]

nucleotide status at end

63
Q

microtubule-associated proteins (MAPs)

A

influence the assembly and stability of microtubules

64
Q

Two groups of MAPs

A
  1. stabilizes microtubules

2. destabilizes

65
Q

domains fo stabilizing MAPs

A
  1. basic microtubule binding domain

2. acidic projection domain

66
Q

Popular microtubule drugs

A
  1. Nocodazole (depol)
  2. Colchicine (depol)
  3. Taxol (stabilizes; anti cancer drug)
67
Q

two families of motor proteins

A

kinesins and dyneins

68
Q

microtubule trasnport is…

A

bidirectional

Therfore, two kinds of motor proteins

69
Q

Vesicle attachment is..

A

ATP dependent

70
Q

translocation is…

A

ATP hydrolysis dependent

71
Q

what is required for vesicle attachment/movement?

A

cytosolic fator

72
Q

kinesin

A

(+) end directed microtubule motor protein

10 different kinds

73
Q

Head of kinesin binds to

A

+MT (Btubulin), ATP

74
Q

Tail of kinesin binds to

A

cargo (vesicle)

75
Q

dyneins

A

-end directed motors for microtubules

can’t mediate cargo transport by itself - required dynactin

76
Q

dynactin

A

helper protein for dyneins

binds to MT vesicles

77
Q

The mitotic apparatus is…

A

a microtubule machine for separating chromosomes

78
Q

mitotic apparatus parts

A

mitotic spindle and pair of asters

79
Q

mitotic spindle

A

bilaterallay symmetric bundle of microtubules and associated proteins with the overall shape of a football

80
Q

aster

A

radial array of microtubules at each pole of the spindle

81
Q

duplicated centrosomes align and begin sep in…

82
Q

centrosome movement during mitosis by..

A

kinesin and dynein

83
Q

Attachment of microtubule to the sister chromatids by

A

kinetochore complex

84
Q

Capture of chromosome by…

A

microtubules

85
Q

random capture by…

A

alternate growing and shrinking of microtubules

86
Q

What follows the random capture at kinetochore complex?

A

chromosome sliding toward the +end of MT using kinetochore associated +end motor

87
Q

Stabilization of chromosome at cell equator

A
  1. Kinetochore dynein and kinesin at pole pull chromosome toward the pole
  2. chromokinesin push chromosome away from pole
  3. treadmilling of tubulin subunits stabilizes the length of the spindle MT
88
Q

Early anaphase

A

depolymerization of MT at +end (as revealed by bleaching experiment)

89
Q

anaphase chromosomes … and the spindle…

A

separate, elongates

90
Q

observation from bleaching experiment

A

distance between bleach and pole remains same (no depol at -end)
distance btw bleach and +end decrease (depol at +end)

91
Q

late anaphase

A

spindle elongation and movement at poles

92
Q

outward movement of centrioles by…

A

dynein attached to cell membrane

93
Q

outward movement of centriole…

A

by spindle kinetochores

94
Q

further elongation of spindle…

A

by MT polymerization

95
Q

Rho signaling promotes…during cytokinesis

A

acto-myosin contraction

96
Q

local activation of RhoA triggers

A

assembly and contraction of contractile ring

97
Q

S-cyclin-CDK initiates DNA…

A

only ONCE/CYCLE

98
Q

Assembly of pre-RC is…

A

inhibited by CDK and facilitated by APC in early G1

99
Q

How does DNA damage block G1 to S progression?

A

by act p53 and stimulating p21 (CKI) transcription

100
Q

p53

A

major tumor-suppresor

101
Q

mitogen

A

extracellular signal molecule that stimulates cells to proliferate
EGF, PDGF, FGF

102
Q

mitogen-activated protein kinase

A

MAP-kinase; protein kinase at the end of a three-component signaling module involved in relaying signals from the plasma membrane to the nucleus

103
Q

without mitogen

A

cells in G1 or G0 (exit cell cycle)

104
Q

mitogens stimulate

A

G1 to S phase progression
increase in G1/S cyclins
increase in S-cyclins
decrease in CKI

105
Q

the most vital checkpoint

106
Q

anaphase promoting complex (APC) controls

A

degradation of mitotic cyclins and exit from mitosis

107
Q

S phase entry

A
  • mitogens stim MAPK activation
  • immediate early gen (fos, Jun) exp
  • turn on Myc exp ->cyclin D exp
  • activate CDK4/6 -> Rb phos
  • > S-phase gene transcription by E2F
108
Q

myc

109
Q

Rb

A

tumor suppressor

110
Q

Growth and division

A

usually coordinated

EXCEPT: muscle cells, frog eggs

111
Q

What limits cell proliferation?

112
Q

Abnormal proliferation cues

A

cell cycle arrest/apoptosis

113
Q

Cell cycle arrest or apoptosis induced by

A

excessive stimulation of mitogenic pathways

114
Q

unintentional cell death

115
Q

intentional cell death

116
Q

autophagy

A

cell eating itself

117
Q

what eats apoptotic cells?

A

macrophages or neutrophils

118
Q

apoptotic cells are…

A

biochemically recognizable

119
Q

biochemical signature of apoptotic cells

A
  1. phosphatidylserine flip from inner to outer (signal to macrophages)
  2. DNA fragmentation
120
Q

TUNEL

A

dUTP nick end labeling (TUNEL) is a method for detecting DNA fragmentation by labeling the terminal end of nucleic acids.

121
Q

annexin V

A

detects phosphatidylserine flip

122
Q

caspase

A

proteases; mediators of apoptosis
C-cysteine
ASP - aspartic acid
ASE - cuts

123
Q

cleavage of caspase

A

into active form by another caspase

124
Q

Types of caspases

A

inflammation - 1,4,5
apoptosis:
initiator - 2,8,9,10
executioner - 3,6,7

125
Q

extrinsic pathway

A

extracellular to apoptosis

can invoke intrinsic for greater response

126
Q

intrinsic pathway

A

intracellular signal to apoptosis

127
Q

apoptosis depends on

A

intracellular proteolytic cascade mediated by caspases

128
Q

E2F protein

A

gene regulatory protein that switches on many genes that encode proteins required for entry into the S phase of the cell cycle

129
Q

death receptor

A

transmembrane receptor protein that can signal the cell to undergo apoptosis when it binds its extracellular ligand
-extrinsic pathway

130
Q

Fas ligand

A

binds to Fas death receptor to assemble DISC

131
Q

DISC

A

death-inducing signaling complex

Fas death receptors, intracellular adaptor proteins and initiator procaspases

132
Q

intrinsic pathway of apoptosis

A

depends on the release into the cytosol of mitochondrial proteins that normally reside in the intermembrane space of these organelles.
- involves cytochrome c from mitochondria

133
Q

Release of cytochrome C activates

A

caspase C chain through APAF (apoptotic protease activating factor-1)

134
Q

apoptosome

A

wheel like heptamer of Apaf1
recruit initiator procaspase proteins
then activate downstream executioner procaspases to induce apoptosis

135
Q

BCL2 family proteins

A

regulators of apoptosis

136
Q

How does extrinsic promote intrinsic?

A

converts one of the Bcl2 proteins and cuts to truncated always active form…

137
Q

IAPs

A

inhibit caspases

138
Q

inhibitors of apoptosis (IAPs)

A

intracellular protein - inhibitors of apoptosis

139
Q

anti-IAPs

A

produced in response to various apoptotic signals

IAP-binding motif

140
Q

anti-IAPs are released from

A

mitochondrial intermembrane space when the intrinsic pathway of apoptosis is activated blocking IAPs in the cytosol and thereby promoting apoptosis

141
Q

survival factor

A

extracellular signal that promotes cell survival by inhibiting apoptosis

142
Q

Hid

A

anti-IAP protein

143
Q

phosphorylation of Hid

A

survival factor activates MAP-kinase

apoptosis blocked

144
Q

Akt kinase

A

serine/threonine protein kinase

145
Q

three ways that extracellular survival factors can inhibit apoptosis

A

A. increased production of anti-apoptotic Bcl2 protein
B. inactivation of pro-apoptotic BH3-only Bcl2 protein
C. inactivation of anti-IAPs

146
Q

activation of AKT kinase

A

activates Bcl2 and inactivates Bad

apoptosis blocked

147
Q

stimulation of transcription of genes that encode anti-apop Bcl2

A

apoptosis blocked

148
Q

too much apoptosis

A

tissue damage - heart attacks, strokes

149
Q

too little apoptosis

A

accumulation of cells - autoimmune

tumors

150
Q

Bcl2 gene

A

lymphocyte cancer

Molecular Cell Biology (5 decks)

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