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MCB 2050 - Second Half - Mullen > Lecture 2 - nucleus > Flashcards

Lecture 2 - nucleus Flashcards

1
Q

What is the largest organelle?

A

nucleus

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1
Q

Does nuclear size vary between organisms and cell-to-cell?

A

yes

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2
Q

When does the nuclear size increase?

A

during development and in cancer cells

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3
Q

What is the difference in the nucleus between eukaryotes and prokaryotes?

A

euk possess membrane bound nucleus, larger, structurally and functionally more complex interiors, cellular compartmentalization

prok possess a region (nucleiod) where chromosome is located; less DNA, less DNA packaging, and limited to no RNA processing

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4
Q

What are the two main functions of the nucleus?

A
  1. compartmentalization of the cellular genome and its activities
  2. coordination of cellular activities
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5
Q

What does separation of the cytoplasm from the genome allow for?

A

spatial and temporal regulation of gene expression in eukaryotes

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6
Q

When are mRNA’s translated in euk vs prok?

A

prok - mRNA translated while txn is in progress
euk - mRNAs undergo post-tnl processing before being transported out of the nucleus and then translated in cytoplasm or at ER

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7
Q

Which has more gene expression control, euk or pro?

A

euk, the nuclear envelope limits access of txn factors from cytoplasm to genome

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8
Q

What is the nucleoplasm?

A

fluid-filled interior of the nucleus, highly organized

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9
Q

How many subdomains does the nucleoplasm have?

A

over 30 specialized subdomains that participate in specific functions

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10
Q

Are nuclear subdomains membrane bound?

A

no

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11
Q

What is the nucleolus?

A

subdomain in the nucleoplasm

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12
Q

What are some physical characteristics of the nucleolus?

A

irregular shaped, dense and granular in appearance

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13
Q

How many nucleoli are in the nucleus?

A

(1-5) size and number depend on metabolic activity of the cell

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14
Q

What is the relationship between nucleoli and cellular metabolism?

A

as cellular activity increases, protein synthesis increase and the size/number of nucleoli increases

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15
Q

What is the function of the nucleolus?

A

producing ribosomes
- site of ribosomal DNA gene txn, rRNA processing and initial stages of ribosomal subunit assembly

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16
Q

Where does the final assembly of ribosomes take place?

A

cytoplasm

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17
Q

How are chromosomes organized in the nucleus during interphase?

A

discrete subdomains, location of gene is often related to its activity

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18
Q

What are interchromosomal channels?

A

regions between chromosome subdomains that serve as barriers to prevent unwanted DNA-DNA and or DNA protein interactions

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19
Q

What are transcription factories?

A

active genes from different subdomains extend into interchromosomal channels to form txn factories where txn factors are concentrated

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20
Q

What are interchromosomal interactions?

A

“kissing chromosomes” - gene regulatory regions from one chromosome activate genes on another chromosome

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21
Q

What are nuclear speckles?

A

subdomain of the nucleus, where mRNA splicing factors are concentrated

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22
Q

Where are nuclear speckles located?

A

in the nucleus, often in interchromosomal channels next to transcription factories

23
Q

What is a unique characteristic of nuclear speckles?

A

numerous and highly dynamic - often move quickly and grow/shrink and change in number depending on needs of the cell

24
Q

What is the nuclear matrix?

A

nuclear subdomain, insoluble fibrillar-like protein network (mesh) distributed throughout nucleoplasm - analogous to cytoskeleton network in cytoplasm

25
Q

What are the functions of the nuclear matrix?

A

structural role - maintains overall shape of nucleus
serves as scaffold - responsible for organizing nuclear subdomains and anchoring protein factors

26
Q

What is the nuclear envelope?

A

nuclear subdomain, “outside of nucleus”, separates the contents of the nucleus from surrounding cytoplasm

27
Q

What is the function of of nuclear envelope?

A

barrier - requires regulated passage of molecules between nucleus and cytoplasm
establishes unique composition of nucleus and spatially regulates gene expression
provides structural framework for nucleus

28
Q

What are the three parts of the nuclear envelope?

A

nuclear membranes
nuclear lamina
nuclear pore complex

29
Q

What are the nuclear membranes?

A

part of the subdomain nuclear envelope, there are two membranes, inner and outer, arranged in parallel, they are phospholipid bilayers

30
Q

What are the inner and outer nuclear membranes separated by?

A

nuclear envelope lumen (10-50 nm diameter)

31
Q

What is the function of the nuclear membranes?

A

serve as barriers to passage of ions, solutes and macromolecules between nucleus and cytoplasm

32
Q

How do the outer and inner membrane come together in the event of a nuclear pore?

A

a nucleoprotein joins them

33
Q

What is the outer nuclear membrane continuous with?

A

rough endoplasmic reticulum

34
Q

What are attached to the outer nuclear membrane?

A

ribosomes

35
Q

What is the nuclear envelope lumen continuous with?

A

the er lumen

36
Q

is the inner nuclear membrane continuous with anything?

A

no, it has a unique protein composition

37
Q

What is the nuclear lamina?

A

part of the subdomain nuclear envelope, network of mesh long, filament-like proteins

38
Q

What are ABC nuclear lamins evolutionarily related to?

A

proteins that form intermediate filaments in cytoskeleton network

39
Q

What is the function of the nuclear lamina?

A

mechanical support
serves as scaffold for attachment of chromatin and nuclear matrix to nuclear envelop

40
Q

What is the consequence of a mutation in the LAMIN gene

A

mutation in the nuclear lamina
hutchinson gilford progeria syndromes
- premature aging in children
- point mutation in LAMIN A gene leading to truncated lamin protein
- results in destabilization of nuclear lamina

41
Q

What is the nuclear pore complex?

A

subdomain of the nuclear envelope, they are channels in the nuclear nevelope

42
Q

What is the function of NPC’s?

A

regulating trafficking (import and export) of all substances between nucleus and cytoplasm such as small polar molecules, RNAs, and proteins

43
Q

How many NPC’s per nucleus?

A

3000-4000, number of NPC’s related to nuclear activity

44
Q

Is the placement of NPC’s random?

A

no

45
Q

How many proteins make up the NPC?

A

about 40 different proteins

46
Q

What are nucleoporins (Nups)?

A

proteins that make up the NPC

47
Q

Are nups conserved?

A

yes

48
Q

What is the general structure of an NPC?

A

8-fold symmetrical structure
central scaffold
FG nucleoporins
Y-complexes
cytoplasmic filaments
nuclear basket

49
Q

What is the central scaffold and its function?

A

a part of the NPC
- composed of integral trans membrane bound nucleoporins
- anchors NPC to nuclear envelope membranes
- forms aqueous central channel - 20-40 nm wide

50
Q

What are FG nucleoporins and their function?

A

part of the NPC
- inner surface is lined by them
- possess unusual AA comp
- FG domains extend into central channel (forms mesh that limits diffusion of macromolecules larger than 40 kDA
- small molecules move freely through NPC in either direction

51
Q

What is the structure of an FG nucleoporin?

A

hydrophilic polypeptides with short repeats of hydrophobic domains enriched in phe and gly - FG domains

52
Q

What are Y-complexes?

A

a part of the NPC
- includes cytoplasmic ring and nuclear ring
- composed of structural Nups
- linked to central scaffold and cytoplasmic filaments

53
Q

Where are Y-complexes located?

A

NPC’s
- cytoplasmic and nuclear side of NPC

54
Q

What are cytoplasmic filaments?

A

part of the NPC
- long filament shaped Nups that extend into the cytoplasm
- involved in nuclear receptor cargo protein recognition and import from the cytoplasm

55
Q

What is the nuclear basket?

A

part of the NPC
- basket like structure located on nuclear side of NPC
- linked to y-complez nuclear ring

56
Q

What is the funtion of the nuclear basket?

A

nuclear receptor-cargo protein import and export to cytoplasm

MCB 2050 - Second Half - Mullen (14 decks)

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