Cell Nucleus (organelles) Flashcards
1
Q
What gives the nucleus its round shape and also protects the nucleus?
A
nuclear lamina
2
Q
The nuclear membrane is continuous with the membrane of the ____
A
ER
3
Q
The nuclear pore complexes cross ____ _____
A
both membranes
4
Q
What is the equivalent of cytoplasm in the nucleus?
A
Nuclear matrix
5
Q
Nuclear substructures are not membrane bound but they still have ____ _____ in nucleus
A
distinct regions
6
Q
What cell has more than one nucleus?
A
muscle cell
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
8
Q
The outer membrane of the nucleus is covered in ____
A
ribosomes
9
Q
The nucleolus has distinct regions - why is this important?
A
for ribosome production
10
Q
What is the perinuclear space?
A
space between the two nuclear membranes
11
Q
What is the purpose of the nucleolus?
A
rRNA synthesis, ribosome assembly
12
Q
Is the nucleolus membrane bound?
A
No
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
14
Q
What are the contents of the nucleoplasm?
A
lamina, matrix, nuclear particles
15
Q
The perinuclear space is continuous with ____ lumen
A
ER
16
Q
What gives the nucleus its shape?
A
nuclear lamina
17
Q
The nuclear envelope has a ____ lipid bilayer
A
double
18
Q
Transmembrane proteins of inner membrane interact with what?
A
nuclear lamins
19
Q
Transmembrane proteins of outer membrane interact with what?
A
cytoskeletal filaments
20
Q
What is the name of the glycoproteins of the nuclear pore complex?
A
Nucleoporins
21
Q
Name the 3 rings that comprise the nuclear pore complex structure
A
cytoplasmic ring
luminal ring
nuclear ring
22
Q
How many subunits does the cytoplasmic ring (of the nuclear pore complex )have?
A
8
23
Q
How many subunits does the nuclear ring (of the nuclear pore complex) have?
A
8
24
Q
What is the purpose of the nuclear pore complex?
A
To decides what enters and exits the nucleus
25
What is to enter the nucleus via active transport through the NPC?
histones, polymerases, Transcription factors, snRNPs, snoRNPs
26
What exits the nucleus via active transport through the NPC?
mRNA, tRNA, ribosomes
27
What is a carrier protein that is important for nuclear import?
Importin
28
What is a carrier protein that is important for nuclear export?
Exportin
29
In nuclear import, the cargo protein contains what kind of signal?
Nuclear localisation signal (NLS)
30
In nuclear export, the cargo protein contains what kind of signal?
Nuclear export signal (NES)
31
What is ultimately controlling the import and export of all protein complexes through the NPC?
RNA GTPase
32
A protein has to have what sequence to enter the nucleus?
NLS
33
A protein has to have what sequence to exit the nucleus?
NES
34
Importan binds to ____ ____ ____
NLS signal sequence
35
Exportin bind to ____ _____ ____
NES Signal sequence
36
RAS and RAN are examples of what kind of protein?
G protein
37
RAS is inactive when bound to ____
GDP
38
RAS is active when bound to ____
GTP
39
Are GAP and GEF G proteins?
No
40
What is a major difference between RAS and RAN?
Ran does not become inactive or active when bound by GDP or GTP, it just binds to different things
41
GEF converts ____ to ______
GDP to GTP
42
GAP converts ____ to ____
GTP to GDP
43
RAN is important for nuclear ___ and ____
export and import
44
What state is RAN in inside nucleus?
GTP bound state
45
What state is RAN in inside cytoplasm?
GDP bound state
46
Where is GEF located in cell?
In nucleus
47
Where is GAP located in cell?
In cytoplasm
48
In order for importin to bind cargo, RAN is in what state?
RAN does not need to be bound to GDP to go into nucleus with cargo
49
In order for importin to release cargo, RAN is in what state?
GTP bound
50
In order for exportin to bind cargo, RAN is in what state?
GTP bound
51
In order for exportin to release cargo, RAN is in what state?
GDP bound
52
Export proteins only recognize what kind of mRNA and why?
mature - do not want immature and not properly spliced mRNA to be translated
53
What are lamins?
high-tensile proteins that are intermediate filaments in nucleus that maintain cell shape and protect membranes
54
Nuclear lamina is the anchorage site for _____
chromosomes
55
Nuclear lamina act as transcription regulators by binding ____
TFs
56
The nuclear lamina lines the inner surface of the ____ _____
nuclear envelope
57
Nuclear lamina attaches to what two very important things?
integral membrane proteins & nuclear protein channels
58
Why is it important that the nuclear lamina interacts with inner membrane proteins?
so during mitosis the nuclear envelope can break down and reform
59
What lamins form the meshwork for the nuclear lamina?
A, B, C
60
What gene is lamina B from?
LMNB gene
61
what gene is lamina A & C from?
LMNA splice variants
62
Lamina A & C form _____
heterodimers
63
Laminas bind to proteins associated with what kind of chromatin?
Heterochromatin
64
What inner membrane nuclear protein do lamins bind to?
Emerin
65
Describe how chromosomes are arranged inside the nucleus
They are not randomly floating around, they have specific territories they occupy that do not overlap with each other
66
Chromatin fibers are bound directly to ____ ____ and ____ ____ at centromeres and telomeres
inner membrane, nuclear lamina
67
What happens to the lamina during prophase?
Lamin are phosphorylated, dissambling the membrane
68
What is responsible for the phosphorylation of lamin?
Cdk1
69
When lamina is disassembled, what happens to A, B, and C?
A & C are released as free dimers
| B is anchored to inner membrane
70
What happens to lamina during telophase?
Cdk1 is inactivated and the lamin are dephosphorylated so they reassemble
71
What is a laminpathy?
hereditary mutation in lamin gene - this means there will be defects in lamin assembly/attachment to nuclear envelope
72
What could potentially be affected by defects in lamin?
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
What do key words: emerin, contracture, sudden heart failure point to?
Emery-Dreifuss Muscular Dystrophy
74
Symptoms: Contractures (especially in elbows, ankles, neck), muscle weakness and atrophy, heart conduction defects and arrhythmias, sudden heart failure could mean what disease?
Emery-Dreifuss Muscular Dystrophy
75
What mutation causes emery-dreifuss muscular dystrophy?
mutation in emerin or lamin A/C
76
What are contractures?
shortening of muscles or tendons
77
Why does mutation in lamin A/C or emerin cause muscular dystrophy?
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
Key words lamin A/C and CHF (congestive heart failure) are linked to what disease?
Dilated Cardiomyopathy
79
Is lamin A/C mutation a common casue of dilated cardiomyopthy?
No, lots of things can cause it, and lamin A/C mutation is a rare cause
80
What is the mechanism by which lamin A/C mutation can cause dilated cardiomyopathy?
Defected lamin causes fragile nuclear lamina and subsequent cell dea
81
Key words lamin A/C, preLamin A, adipocute accumulation, muscle prominen are linked to what disease?
Lipodystrophy
82
Symptoms: accumulation of adipose tissue in face, neck, muscle prominence, peripheral lipoatrophy, what disease could this be?
lipodystrophy
83
What causes lipid dystrophy?
Not fully understood, Lamin A interacts with TF active with adipocytes, so there is impaired adipocyte differentiation
84
key words: bleb formation, premature cell death, alopecia, prominent eyes, arteriosclerosis point to what disease?
Hutchinson-Gilford Progeria Syndrome
85
What is Ateriosclerosis?
hardening or scarring of blood vessels
86
What is the mode of inheritance for hutchinson-gilford progeria syndrome?
Autosomal dominant - sporadic (it occurs in germline, child will have disorder but themselves are not fertile)
87
What important disease involves cells dying prematurely, resulting in premature aging?
Hutchinson-Gilford progeria syndrome
88
What is the life expectancy of children with Hutchinson-Gilford progeria syndrome?
13 years
89
At what point might you notice a child has Hutchinson-Gilford progeria syndrome?
18-24 months. Before this they will meet normal development/growth curve
90
Describe the mechanism for Hutchinson-Gilford progeria syndrome
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
Why does a mutation in Lamin A cause so many different kinds of disorders?
Lamin A binds to many different things: architectural partners, chromatin partners, gene-regulatory partners, signalling partners.
92
What are the two main nuclear subsctructures?
Nucleoli & Nucleolus
93
If a cell needs a lot of protein it will need a lot of ribosomes, therefore it will need what substructure?
Nucleoli
94
A cell can have a single _____ or multiple nucleoli
nucleolus
95
A cell can have a single nucleolus or multiple ______
nucleoli
96
What does CBs stand for?
Cajal bodies
97
What are snoRNA?
small nucleolar RNA
98
What are snRNA?
small nuclear RNA
99
What to CBs/Gems produce?
non translated RNA (snoRNA & snRNA)
100
Once snoRNA is made in CBs/Gems, what happens?
they go to cytoplasm where they combine with protein and become RNP, then are stored in the nucleolus
101
Once snRNA are made in CBs/Gems, what happens?
They go to cytoplasm where they combine with protein and become RNP, then they are stored in speckles
102
What do speckles do?
store snRNPs, are involved in mRNA modification
103
Do subnuclear structures have membranes?
No
104
Interchromatin granule clusters is another name for
speckles
105
Key words: SMN in Gems, defected snRNP assembly, hypotonia, *most common genetically related neonatal death related to what disease?
Spinal Muscular Atrophy
106
What is the mechanism for spinal muscular atrophy?
Mutated SMN causes defective snRNP assembly subsequent defective pre-mRNA splicing causing loss of motor neurons
107
symptsom: sudden onset, rapid progression; muscle weakness and atrophy, hypotonia, dysphagia and feeding difficulties, RTIs are what disease?
Spinal Muscular Atrophy
108
mode of inheritance for spinal muscular atrophy?
recessive
109
Nucleolus is responsible for what?
ribosome factory! synthesis of rRNA and assembly of ribosomes
110
What processes ribosomes in nucleolus?
snoRNPs
111
snoRNAs are synthesized by ____
RNA pol II
112
How does snoRNP assist in ribosome assembly?
contain snoRNAs - these have complementary base pairs to pre-rRNA, they bind and then enzymes can bind and catalyze base modification like methylation
113
When is the nucleolus assembled, and when does it disassemble?
It is assembled throughout interphase (and normal cell activity) and disassembles during mitosis
114
What does NOR stand for
nuclear organizing region
115
What does the nucleolus form around?
NORs (nuclear organizing region)
116
What is a NOR?
a region of DNA that contains rRNA genes
117
What are the nucleolus substructures?
Fibrillar center, Dense fibrillar components (pars fibrosa), Granular components (pars granulosa) (slide 82)
118
Describe where a fibrillar center is located
the most central part of nucleolus
119
What is in a fibrillar center?
transcriptionally inactive DNA and NORs
120
Another name for dense fibrillar component is?
Pars fibrosa
121
Another name for granular component is?
pars granulosa
122
Where is pars fibrosa located?
Near fibraillar center, but on outside of it
123
What happens at pars fibrosa?
rRNA are transcribed and cleaved and modified by snoRNPs
124
What substructure of the nucleolus are snoRNPs in?
pars fibrosa
125
What happens at the pars granulosa?
Where rRNAs being to assemble with ribosomal proteins (NOTE: they do not complete until they reach cytoplasm)
126
5.8S, 18S, 28S are part of what genes?
rRNA
127
What chromosomes are rRNA genes on?
13, 14, 15, 21, 22
128
45S RNP is a ____ precurser
rRNA
129
45S pre-RNA is spliced into what?
18S, 5.8S, 28S rRNA
130
18S, 5.8S, 28S, 5S - which are part of large/small subunit?
18S - part of 40S small ribosomal subunit
| 5.8S & 28S & 5S - part of 60S large ribosomal subunit
131
how are 5S rRNA transcribed?
outside nucleus, in cytoplasm, by RNA pol III
132
If there is a prominent nucleolus it probably means what?
there is a lot of protein synthesis!
133
What kinds of cells would have an active nucleolus? Give examples
protein-secreting cells
| pancreas, plasma cells, developing haematopoetic precursers, cancer cells
