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MCB1 Block 3 > Cell Nucleus (organelles) > Flashcards

Cell Nucleus (organelles) Flashcards

1
Q

What gives the nucleus its round shape and also protects the nucleus?

A

nuclear lamina

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2
Q

The nuclear membrane is continuous with the membrane of the ____

A

ER

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3
Q

The nuclear pore complexes cross ____ _____

A

both membranes

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4
Q

What is the equivalent of cytoplasm in the nucleus?

A

Nuclear matrix

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5
Q

Nuclear substructures are not membrane bound but they still have ____ _____ in nucleus

A

distinct regions

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6
Q

What cell has more than one nucleus?

A

muscle cell

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7
Q

What is the purpose of the nucleus? ie - why do the contents of the nucleus need to be kept separate from the rest of the cell?

A

protect DNA from harsh cytosolic enviornment
separates ribosomes from mRNA until they are mature
Regulates gene transcription, cell cycle, cytosolic metabolism
Separates substrates and enzymes

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8
Q

The outer membrane of the nucleus is covered in ____

A

ribosomes

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9
Q

The nucleolus has distinct regions - why is this important?

A

for ribosome production

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10
Q

What is the perinuclear space?

A

space between the two nuclear membranes

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11
Q

What is the purpose of the nucleolus?

A

rRNA synthesis, ribosome assembly

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12
Q

Is the nucleolus membrane bound?

A

No

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13
Q

The nuclear envelope is what surrounds the nucleus, name key features of it.

A

2 lipid bilayer membranes
perinuclear space
nuclear pores
compartmentalisation

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14
Q

What are the contents of the nucleoplasm?

A

lamina, matrix, nuclear particles

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15
Q

The perinuclear space is continuous with ____ lumen

A

ER

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16
Q

What gives the nucleus its shape?

A

nuclear lamina

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17
Q

The nuclear envelope has a ____ lipid bilayer

A

double

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18
Q

Transmembrane proteins of inner membrane interact with what?

A

nuclear lamins

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19
Q

Transmembrane proteins of outer membrane interact with what?

A

cytoskeletal filaments

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20
Q

What is the name of the glycoproteins of the nuclear pore complex?

A

Nucleoporins

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21
Q

Name the 3 rings that comprise the nuclear pore complex structure

A

cytoplasmic ring
luminal ring
nuclear ring

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22
Q

How many subunits does the cytoplasmic ring (of the nuclear pore complex )have?

A

8

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23
Q

How many subunits does the nuclear ring (of the nuclear pore complex) have?

A

8

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24
Q

What is the purpose of the nuclear pore complex?

A

To decides what enters and exits the nucleus

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25
Q

What is to enter the nucleus via active transport through the NPC?

A

histones, polymerases, Transcription factors, snRNPs, snoRNPs

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26
Q

What exits the nucleus via active transport through the NPC?

A

mRNA, tRNA, ribosomes

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27
Q

What is a carrier protein that is important for nuclear import?

A

Importin

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28
Q

What is a carrier protein that is important for nuclear export?

A

Exportin

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29
Q

In nuclear import, the cargo protein contains what kind of signal?

A

Nuclear localisation signal (NLS)

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30
Q

In nuclear export, the cargo protein contains what kind of signal?

A

Nuclear export signal (NES)

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31
Q

What is ultimately controlling the import and export of all protein complexes through the NPC?

A

RNA GTPase

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32
Q

A protein has to have what sequence to enter the nucleus?

A

NLS

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33
Q

A protein has to have what sequence to exit the nucleus?

A

NES

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34
Q

Importan binds to ____ ____ ____

A

NLS signal sequence

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35
Q

Exportin bind to ____ _____ ____

A

NES Signal sequence

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36
Q

RAS and RAN are examples of what kind of protein?

A

G protein

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37
Q

RAS is inactive when bound to ____

A

GDP

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38
Q

RAS is active when bound to ____

A

GTP

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39
Q

Are GAP and GEF G proteins?

A

No

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40
Q

What is a major difference between RAS and RAN?

A

Ran does not become inactive or active when bound by GDP or GTP, it just binds to different things

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41
Q

GEF converts ____ to ______

A

GDP to GTP

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42
Q

GAP converts ____ to ____

A

GTP to GDP

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43
Q

RAN is important for nuclear ___ and ____

A

export and import

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44
Q

What state is RAN in inside nucleus?

A

GTP bound state

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45
Q

What state is RAN in inside cytoplasm?

A

GDP bound state

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46
Q

Where is GEF located in cell?

A

In nucleus

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47
Q

Where is GAP located in cell?

A

In cytoplasm

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48
Q

In order for importin to bind cargo, RAN is in what state?

A

RAN does not need to be bound to GDP to go into nucleus with cargo

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49
Q

In order for importin to release cargo, RAN is in what state?

A

GTP bound

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50
Q

In order for exportin to bind cargo, RAN is in what state?

A

GTP bound

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51
Q

In order for exportin to release cargo, RAN is in what state?

A

GDP bound

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52
Q

Export proteins only recognize what kind of mRNA and why?

A

mature - do not want immature and not properly spliced mRNA to be translated

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53
Q

What are lamins?

A

high-tensile proteins that are intermediate filaments in nucleus that maintain cell shape and protect membranes

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54
Q

Nuclear lamina is the anchorage site for _____

A

chromosomes

55
Q

Nuclear lamina act as transcription regulators by binding ____

A

TFs

56
Q

The nuclear lamina lines the inner surface of the ____ _____

A

nuclear envelope

57
Q

Nuclear lamina attaches to what two very important things?

A

integral membrane proteins & nuclear protein channels

58
Q

Why is it important that the nuclear lamina interacts with inner membrane proteins?

A

so during mitosis the nuclear envelope can break down and reform

59
Q

What lamins form the meshwork for the nuclear lamina?

A

A, B, C

60
Q

What gene is lamina B from?

A

LMNB gene

61
Q

what gene is lamina A & C from?

A

LMNA splice variants

62
Q

Lamina A & C form _____

A

heterodimers

63
Q

Laminas bind to proteins associated with what kind of chromatin?

A

Heterochromatin

64
Q

What inner membrane nuclear protein do lamins bind to?

A

Emerin

65
Q

Describe how chromosomes are arranged inside the nucleus

A

They are not randomly floating around, they have specific territories they occupy that do not overlap with each other

66
Q

Chromatin fibers are bound directly to ____ ____ and ____ ____ at centromeres and telomeres

A

inner membrane, nuclear lamina

67
Q

What happens to the lamina during prophase?

A

Lamin are phosphorylated, dissambling the membrane

68
Q

What is responsible for the phosphorylation of lamin?

A

Cdk1

69
Q

When lamina is disassembled, what happens to A, B, and C?

A

A & C are released as free dimers

B is anchored to inner membrane

70
Q

What happens to lamina during telophase?

A

Cdk1 is inactivated and the lamin are dephosphorylated so they reassemble

71
Q

What is a laminpathy?

A

hereditary mutation in lamin gene - this means there will be defects in lamin assembly/attachment to nuclear envelope

72
Q

What could potentially be affected by defects in lamin?

A

there is a fragile nuclear envelope, so muscle fibers, bones, skin, CT can be affected
can have disruption of nuclear function - TFs are altered

73
Q

What do key words: emerin, contracture, sudden heart failure point to?

A

Emery-Dreifuss Muscular Dystrophy

74
Q

Symptoms: Contractures (especially in elbows, ankles, neck), muscle weakness and atrophy, heart conduction defects and arrhythmias, sudden heart failure could mean what disease?

A

Emery-Dreifuss Muscular Dystrophy

75
Q

What mutation causes emery-dreifuss muscular dystrophy?

A

mutation in emerin or lamin A/C

76
Q

What are contractures?

A

shortening of muscles or tendons

77
Q

Why does mutation in lamin A/C or emerin cause muscular dystrophy?

A

Defect in lamin assembly/attachment to nuclear envelope causes fragile nuclear envelope resulting in disruption of nuclear function: aberrant distribution of chromosomes is altered

78
Q

Key words lamin A/C and CHF (congestive heart failure) are linked to what disease?

A

Dilated Cardiomyopathy

79
Q

Is lamin A/C mutation a common casue of dilated cardiomyopthy?

A

No, lots of things can cause it, and lamin A/C mutation is a rare cause

80
Q

What is the mechanism by which lamin A/C mutation can cause dilated cardiomyopathy?

A

Defected lamin causes fragile nuclear lamina and subsequent cell dea

81
Q

Key words lamin A/C, preLamin A, adipocute accumulation, muscle prominen are linked to what disease?

A

Lipodystrophy

82
Q

Symptoms: accumulation of adipose tissue in face, neck, muscle prominence, peripheral lipoatrophy, what disease could this be?

A

lipodystrophy

83
Q

What causes lipid dystrophy?

A

Not fully understood, Lamin A interacts with TF active with adipocytes, so there is impaired adipocyte differentiation

84
Q

key words: bleb formation, premature cell death, alopecia, prominent eyes, arteriosclerosis point to what disease?

A

Hutchinson-Gilford Progeria Syndrome

85
Q

What is Ateriosclerosis?

A

hardening or scarring of blood vessels

86
Q

What is the mode of inheritance for hutchinson-gilford progeria syndrome?

A

Autosomal dominant - sporadic (it occurs in germline, child will have disorder but themselves are not fertile)

87
Q

What important disease involves cells dying prematurely, resulting in premature aging?

A

Hutchinson-Gilford progeria syndrome

88
Q

What is the life expectancy of children with Hutchinson-Gilford progeria syndrome?

A

13 years

89
Q

At what point might you notice a child has Hutchinson-Gilford progeria syndrome?

A

18-24 months. Before this they will meet normal development/growth curve

90
Q

Describe the mechanism for Hutchinson-Gilford progeria syndrome

A

Defect in lamin causes fragile nuclear envelope (bleb formation, loss of peripheral heterochromatin, NPC clustering) resulting in progressive nuclear damage and premature cell death

91
Q

Why does a mutation in Lamin A cause so many different kinds of disorders?

A

Lamin A binds to many different things: architectural partners, chromatin partners, gene-regulatory partners, signalling partners.

92
Q

What are the two main nuclear subsctructures?

A

Nucleoli & Nucleolus

93
Q

If a cell needs a lot of protein it will need a lot of ribosomes, therefore it will need what substructure?

A

Nucleoli

94
Q

A cell can have a single _____ or multiple nucleoli

A

nucleolus

95
Q

A cell can have a single nucleolus or multiple ______

A

nucleoli

96
Q

What does CBs stand for?

A

Cajal bodies

97
Q

What are snoRNA?

A

small nucleolar RNA

98
Q

What are snRNA?

A

small nuclear RNA

99
Q

What to CBs/Gems produce?

A

non translated RNA (snoRNA & snRNA)

100
Q

Once snoRNA is made in CBs/Gems, what happens?

A

they go to cytoplasm where they combine with protein and become RNP, then are stored in the nucleolus

101
Q

Once snRNA are made in CBs/Gems, what happens?

A

They go to cytoplasm where they combine with protein and become RNP, then they are stored in speckles

102
Q

What do speckles do?

A

store snRNPs, are involved in mRNA modification

103
Q

Do subnuclear structures have membranes?

A

No

104
Q

Interchromatin granule clusters is another name for

A

speckles

105
Q

Key words: SMN in Gems, defected snRNP assembly, hypotonia, *most common genetically related neonatal death related to what disease?

A

Spinal Muscular Atrophy

106
Q

What is the mechanism for spinal muscular atrophy?

A

Mutated SMN causes defective snRNP assembly subsequent defective pre-mRNA splicing causing loss of motor neurons

107
Q

symptsom: sudden onset, rapid progression; muscle weakness and atrophy, hypotonia, dysphagia and feeding difficulties, RTIs are what disease?

A

Spinal Muscular Atrophy

108
Q

mode of inheritance for spinal muscular atrophy?

A

recessive

109
Q

Nucleolus is responsible for what?

A

ribosome factory! synthesis of rRNA and assembly of ribosomes

110
Q

What processes ribosomes in nucleolus?

A

snoRNPs

111
Q

snoRNAs are synthesized by ____

A

RNA pol II

112
Q

How does snoRNP assist in ribosome assembly?

A

contain snoRNAs - these have complementary base pairs to pre-rRNA, they bind and then enzymes can bind and catalyze base modification like methylation

113
Q

When is the nucleolus assembled, and when does it disassemble?

A

It is assembled throughout interphase (and normal cell activity) and disassembles during mitosis

114
Q

What does NOR stand for

A

nuclear organizing region

115
Q

What does the nucleolus form around?

A

NORs (nuclear organizing region)

116
Q

What is a NOR?

A

a region of DNA that contains rRNA genes

117
Q

What are the nucleolus substructures?

A

Fibrillar center, Dense fibrillar components (pars fibrosa), Granular components (pars granulosa) (slide 82)

118
Q

Describe where a fibrillar center is located

A

the most central part of nucleolus

119
Q

What is in a fibrillar center?

A

transcriptionally inactive DNA and NORs

120
Q

Another name for dense fibrillar component is?

A

Pars fibrosa

121
Q

Another name for granular component is?

A

pars granulosa

122
Q

Where is pars fibrosa located?

A

Near fibraillar center, but on outside of it

123
Q

What happens at pars fibrosa?

A

rRNA are transcribed and cleaved and modified by snoRNPs

124
Q

What substructure of the nucleolus are snoRNPs in?

A

pars fibrosa

125
Q

What happens at the pars granulosa?

A

Where rRNAs being to assemble with ribosomal proteins (NOTE: they do not complete until they reach cytoplasm)

126
Q

5.8S, 18S, 28S are part of what genes?

A

rRNA

127
Q

What chromosomes are rRNA genes on?

A

13, 14, 15, 21, 22

128
Q

45S RNP is a ____ precurser

A

rRNA

129
Q

45S pre-RNA is spliced into what?

A

18S, 5.8S, 28S rRNA

130
Q

18S, 5.8S, 28S, 5S - which are part of large/small subunit?

A

18S - part of 40S small ribosomal subunit

5.8S & 28S & 5S - part of 60S large ribosomal subunit

131
Q

how are 5S rRNA transcribed?

A

outside nucleus, in cytoplasm, by RNA pol III

132
Q

If there is a prominent nucleolus it probably means what?

A

there is a lot of protein synthesis!

133
Q

What kinds of cells would have an active nucleolus? Give examples

A

protein-secreting cells

pancreas, plasma cells, developing haematopoetic precursers, cancer cells

MCB1 Block 3 (15 decks)

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