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Anat 262 > Lecture 6 > Flashcards

Lecture 6 Flashcards

1
Q

Largest organelle

A

Nucleus

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2
Q

Organization of the nucleus starting from the cytoplasm?

A
  1. Nuclear envelope
  2. Nuclear lamina
  3. Nuclear interior
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3
Q

Nuclear envelope structure?

A

Outer nuclear membrane
Perinuclear space
Inner nuclear membrane

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4
Q

T/F: Inner/outer nuclear membranes differ in the proteins they carry

A

True

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5
Q

Nuclear pore complex?

A

Found at the junction of the inner and outer nuclear membranes, these mediate trafficking of most material in/out of the nucleus

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6
Q

Components of the nuclear interior?

A

Nucleolus
Chromatin
Nuclear bodies
Nuclear matrix

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7
Q

What is the nucleolus?

A

Complex compartment formed by phase separation

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8
Q

What are nuclear bodies?

A

Large variety of compartments within the nucleoplasm that don’t have a membrane and form by phase separation
-Involved in splicing and DNA repair

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9
Q

Nuclear matrix?

A

Filamentous system within the nucleus

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10
Q

T/F: Outer nuclear membrane is continuous with the ER?

A

True

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11
Q

T/F: perinuclear space is continuous with the ER lumen?

A

True

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12
Q

Heterochromatin vs Euchromatin in the nucleus?

A

Heterochromatin is close to the nuclear envelope whereas euchromatin is in the middle of the nucleus

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13
Q

Does the nucleolus have a membrane?

A

No

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14
Q

How many nucleoli do mammalian cells have?

A

2-3

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15
Q

Functions of the nucleoli?(9)

A
  1. Produce/process 47S rRNA
  2. Assemble ribosomal subunits(both)
  3. Assemble signal recognition particle
  4. Regulate aptosis (cell death)
  5. Regulate progression through the cell cycle
  6. Control the function of p53
  7. Control telomerase function
  8. Regulate stress response
  9. Viruses replicate in the nucleoli
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16
Q

Compartments of the nucleolus formed by phase separation?

A

1.Granular compartment
2. Dense fibrillar component embedded in GC
3. Fibrillar component embedded in DFC(RNA pol 1 for 47S rRNA)

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17
Q

How is 47S rRNA precursor synthesized?

A
  1. RNA-pol I which generates the 47S rRNA precursor is found in the fibrillar component of the nucleoli
  2. RNA pol I trascribes the RNA precursor 47S at the border of the FC and DFC
  3. This transcript then moves through the nucleolus where it is processed and proteins are added
  4. Now we have a ribosomal subunit that matures outside the nucleolus
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18
Q

Where is nucleophosmin(NPM) found?

A

Granular component of the nucleolus

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19
Q

Properties of phase separation?

A

Drop like

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20
Q

How to test for phase separation?

A
  1. Place FBL and NPM in a test tube and mix them
  2. They generate droplets in the tube(LLPS occurs)
  3. These droplets are not uniform some compartments contain NPM and other FBL (this proves they tend to separate from each other)
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21
Q

What is FBL(fibrillation)?

A

Protein found in the dense fibrillar component of the nucleolus

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22
Q

Four types of rRNA?

A
  1. 28S
  2. 5.8S
  3. 5S
  4. 18S
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23
Q

What rRNA make up the 47S precursor?

A

5.8S, 28S and 18S

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24
Q

How many copies of rRNA genes do we have?

A

10

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25
Nucleolar Organizers?
Contain active rRNA genes, the transcripts will then form in the nucleoli
26
Processing the rRNA?
Involves cutting pre rRNA into the 28S, 18S and 5.8S
27
Where is 5S rRNA made?
Nucleoplasm
28
Why don't we do protein translation in the nucleus?
1. Don't want to make proteins that chew up DNA 2. If we have huge complex that we need to assemble for the cytoplasm we may not be able to get it across the NPC 3. In the nucleus we have unspliced and different intermediates of mRNA whereas in the cytoplasm we have properly splice mRNA , if we use unspliced mRNA this will make useless protein(could be potentially toxic)
29
Why do patients with cancer have large nucleoli?
They need a lot of rRNA to make a lot of ribosomes and protein which help the cancer cells to divide
30
NPC mass?
120MD
31
Structure of the NPC
Has 8 fold symmetry has a central gated channel in the middle
32
Role of NPC
Active transport and diffusion
33
Size of molecules that can diffuse through NPC?
smaller than 40kDa
34
Size of molecules transported through NPC via active diffusion?
Larger than 40kDa
35
Proteins in the NPC
-8 fold symmetry each slice has a set of different protein -Each slice has 35 different proteins but these 35 different proteins can come various in copies of 1, 2, 3, 4, 5, etc. in each slice -Each NPC has about 100 proteins
36
Nucleoporins
-Proteins in the NPC -Can come with repeats or without -NUP and then a number
37
FXF repeats nucleoporins?
Have several copies of this repeat sequence and are able to undergo phase separation Involved in transport in/out of the nucleus
38
GFLF repeat nucleoporins?
-RNA transport
39
No repeat nucleoporins?
-Anchor the NPC to the membrane
40
Nuclear Lamina
-Under the inner nuclear membrane -Composed of lamina which are intermediate filaments
41
Filamentous vs non filamentous nuclear lamina?
Filamentous lamins underly the nuclear membrane Non-filamentous are within the nucleus
42
Nuclear Lamina connection?
Connects to the inner nuclear membrane and with the chromatin
43
LBR (nuclear envelope protein)
Protein in the inner nuclear membrane that contacts the nuclear lamina which contacts chromatin -Multiple transmembrane domains -Lamin binding domain and chromatin binding domain
44
LAP2
Proteins in the inner nuclear membrane that contacts both the lamina and the chromatic -One transmembrane domain, laminin binding domain, chromatin binding domain
45
Two proteins that allow nucleus and cytoplasm to communicate?
SUN and KASH
46
SUN Proteins?
In the inner nuclear membrane, have large domains in the perinuclear space that interact with KASH
47
KASH proteins
In the outer nuclear membrane Have large domains in the cytoplasm
48
LINC complexes?
Contact between inner/outer nuclear membrane proteins Links the nucelus and cytoplasm
49
Do KASH proteins interact with proteins in the cytoplasm?
Yes, they interact with actin/microtubules
50
Why connect the nucleoskeleton and cytoskeleton?
-Makes it possible to deform the nucleus to move large complexes across the tissue -Cell migration relies on changing the shape of a cell or shape of the nucleus, the communication between the nucleoplasm and the cytoskeleton(which is organizing the shape of the nucleus) allows the cell to deform and allow for migration
51
How are nuclear lamins different from other intermediate filaments?
Nuclear localization
52
Lamin formation
1. Lamin monomers associate into dimers (both heads facing same way) 2. Head-to-tail association occurs between dimers forming polymers 3. Polymers associate into higher structures
53
What happens to nuclear lamins during mitosis when they need to be disassembled?
Both the head and tail domains of the higher structures are phosphorylated which causes the filaments to fall apart. At the end of mitosis we dephosphorylated
54
Two families of lamins?
LaminA : Soluble in mitosis LaminB: Remain associated with membranes during mitosis
55
How many Lamin A genes are there?
One, to get different type sof lamin A we splice them differently
56
How lamin B geness are there ?
2 (LMNB1, LMNB2)
57
Expression of lamin A?
Controlled by differentiation , primarily found in differentiated cells
58
Where are lamin B found?
Associated with membranes since they have modified C-terminus
59
Mature Lamin A
Long C-terminus and at the end a CaaX motif -Two cleavage sites
60
Lamin C
-Splice variant of lamin A gene -No cleavage sites or CaaX motif
61
Lamin B
-Always has CaaX at the C-terminus
62
Farnesyl Moieties?
-Three copies of Isoprenyl that are covalently linked make up the farnesyl moiety -This moiety is put on the cysteine which is sitting at the C-terminus(CaaX) -C amino acid becomes modified with the farnesyl
63
Prupose of modifying the C-terminal and then cleaving it off?
Use this complex processing scheme to have the lamin in various locations where it may associate/contribute to different functions. Some of these functions probably have something to do with things going on in the nuclear membrane.
64
A-type Lamin binding partners?
-Nuclear architecture(proteins of inner nuclear membrane) -Histones -Gene regulation -Signaling
65
Would a lamin A/C knockout mous be alive?
Yes, lamin A functions can be compensated by using lamin B
66
T/F: mutant lamin A can be worse than knockout?
True
67
Hutchinson Gilford Progeria
Mutation in the C-terminus of lamin A creates progerin which retains hydrophobic moiety at the C-terminus
68
What is Hutchinson Progeria?
Patients prematurely age/die
69
How can lamin A mutations alter different cell types?
1. Lamin A mutationsaffect mechanical properties of the nucleus 2. Lamin A plays a role in gene expression and can modulate expression of certain genes
70
How can heart cells be affected by LMNA mutations?
Lamina supports the structure/organization of the nucleus when the heart is constantly contracting and the lamin a is weak these cells are prone to be damaged or even die

Anat 262 (8 decks)

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