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The Nucleus Flashcards

1
Q

General functions of the nucleus

A

Storage of DNA
DNA to rNA transcription
Mechanical element- stiffer than rest of the cell

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2
Q

How is genetic material arranged in eukaryotes

A

compartmentalised

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3
Q

Benefits of compartmentalisation

A
  • protect DNA
  • incr SA for membrane-localised reactions
  • Incr efficiency of transcription and synthesis
  • More ways to regulate gene expression
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4
Q

Nuclear double membrane: what is it continuous with?

A

Lumen of ER

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5
Q

Nuclear lamina- related to

A

intermediate filaments- most recent common ancestor

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6
Q

Nuclear lamina: location

A

form meshwork on inner nuclear membrane

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7
Q

What does nuclear lamina associate with

A

DNA

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8
Q

Two types of nuclear lamina

A

A/C and B

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9
Q

Nuclear structure: LINC complex

A

Protein complex

Links nuclear lamina with cytoskeleton

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10
Q

LINC proteins on inner membrane (TM)

A

SUN/KASH

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11
Q

LINC proteins on outer membrane (TM)

A

Nesprins, connect to different cytoskeleton elements eg actin- 4 different types

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12
Q

What is the nucleoskeleton/ nuclear matrix made up of

A

NuMa, Titin, Spectrin,PLF, Nuclear actin, Motor proteins

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13
Q

NuMa protein

A

Nuclear mitotic apparatus 1, very large

Organisation of chromatin

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14
Q

Titin protein

A

binds chromosomes and lamina

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15
Q

Spectrin protein

A

Elastic component of lamina

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16
Q

PLF

A

pore linked filaments

important in trafficking

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17
Q

Nuclear actin

A

in form of short filaments or monomers of (G-actin)

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18
Q

Motor proteins

A

Nuclear myosin, kinase

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19
Q

Chromosomes

A

DNA-protein complexes specially packaged for cell division

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20
Q

Chromatin

A

complex of DNA, RNA and proteins

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21
Q

Euchromatin

A 
'true' chromatin
less visible by microscopy
not so densely packed
majority of the genome -90%
localised in central part of the nucleus
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22
Q

Heterochromatin

A

‘different’ chromatin
Looks dark under microscope
Tightly packed condensed DNA
Localised around lamina and nucleoli

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23
Q

What does localisation within the nucleus affect

A

affects whether genes are expressed

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24
Q

Export of RNA and ribosomes

A

mRNA- messenger
rRNA- ribosomal
tRNA- transfer
Assembled ribosomal units

25
Import proteins from the cytoplasm
RNA poly RIbosomal proteins TFs Other structural proteins eg lamins
26
Nuclear pore complex
Ring structure with 8 fold symmetry 30 different kinds of Nups (nuclear pore proteins) Central channel filled with FG-Nups that form selective barrier to transport Common ancestry with COPI, COPII and clathrin Nuclear side there is a basket, and on the cytosolic side there are fibrils
27
Two kinds of movement through the NPC
passive- small molecules and proteins | Facilitated- RNAs, large proteins and macromolecular complexes
28
Energy for facilitated transport from
ATP hydrolysis for mRNA | GTP hydrolysis for proteins, tRNA and ribosomes
29
What does facilitated transport require (excluding energy)
nucelar transport receptors: karyopherins
30
mRNP
mRNA-protein complex | includes proteins tat bind to the mRNA involved in its processing, capping, splicing proteins as well as export factors
31
How can mRNP get in and out
through NPC
32
What does ATP hydrolysis do in mRNP transport through NPC
Release of Dbp5 in cytoplasm and mRNP remodelling so it can't go back in because not energetically favourable
33
Another name for karyopherins
Importins
34
Karyopherins
bind cargo proteins in cytoplasm- recognise NLS Interact with FG-Nups Move through NPC and release cargos in nucleus
35
What is cargo release enabled by (importin)
Ran-GTP binding to importin- Beta | conformational change that results in complex coming apart
36
Exportins
Bind cargo proteins in the nucleus when they (the exportin) are bound to Ran-GTP Interact with FG-Nups Release cargos in cytoplasm
37
What is cargo loading enabled by
Ran GTP binding to exportin Conformational change that results in complex assembly Ran GTP hydrolysed to Ran GDP in cytoplasm for dissociation
38
GTPases
molecular switches | bind GTP, hydrolyse a phosphate to form GDP
39
What type of Ran in the cytosol
Ran-GAP
40
What type of Ran in the nucleus
Ran-GEF
41
GAP assists
GTP hydrolysis to GDP | useful diagram
42
GEF assists
GTP loading after hydrolysis
43
NLS
``` nuclear localisation sequence 8 AAs long Can occur anywhere in a protein Lysine (K), arginine (R) and Proline (P) binds to importins ```
44
NES
nuclear export signal | Sequence with 4 hydrophobic AAs (most often leucine, L)
45
How can NLS and NES be modified
phosphorylation etc
46
nucleoli
little nuclei not visible under microscope | no membranes
47
Nucleolus
cells can have 1 large nucleolus or many small nucleoli
48
Nucleolus major functions
Transcription of rRNAs | Assembly of ribosomal subunits
49
Nucleolus composed of
segments of 10 chromosomes encoding rRNA genes Proteins for processing rRNAs Ribosomal subunit proteins SnoRNA (small nucleolar RNA)
50
SnoRNA
oligonucleotides that help process rRNA
51
Other functions nucleolus
sensing and responding to stress | Cell cycle regulation- cancer it goes worong
52
Cajal bodies
RNA processing Genome organisation Dense foci of coilin protein- resemble coiled balls of yarn under EM
53
PML bodies
Associated often with cajal bodies | DNA repair, cell proliferation, programmed cell death
54
Speckles
``` Gene transcription mRNA processing (splicing ) ```
55
Evolution of the nucleus theory
DNA in ancient prokaryotic cell tethered to membrane Over time tethering increased till nucleus bound DNA Evidence for this theory- a lot of the proteins found linking the DNA to the inner mem have evol relationships to COP proteins involved in trafficking
56
Mutations in lamins give rise to
laminopathies muscular cystrophy and progeria result from mechanical failure as without lamina don't have structural protection
57
what are euchromatin and heterochormatin also referred to as
A/B chromatin
58
LADs
lamina associated domains
59
Level of RNA production in LADs
less RNA production in LADs (ie where heterochromatin is) than away from lamins (euchromatin)

BB10005 (27 decks)

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