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Cell biology - BB10005 > lecture 1 - the nucleus > Flashcards

lecture 1 - the nucleus Flashcards

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1
Q

What are the 3 general functions of the nucleus?

A
  • storage of DNA
  • Transcription of RNA from DNA
  • Mechanical element as it is stiffer than the rest of the cell
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2
Q

What is one key component of eukaryotic cells?

A

genetic material is compartmentalised

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3
Q

What are the benefits of compartmentalisation?

A
  • Protect DNA – critical information storage
  • Increase surface area for membrane-localised reactions
  • Increase efficiency of transcription and synthesis
  • More ways to regulate gene expression
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4
Q

What is a significant structure if the nuclear double membrane?

A

Its continuous with the double membrane

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5
Q

what is one theory about how the nucleus may have evolved?

A
  • DNA in prokaryotes is tethered

- over time the tethering increases until nucleus is bound

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6
Q

What is the nuclear lamina?

A

thin plate, slice or layer that is related to intermediate filaments to form meshwork on inner nuclear membrane

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7
Q

What are the two types of nuclear lamina?

A

A/C and B

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8
Q

What are the main diseases caused when the lamina is destroyed?

A

muscular dystrophy and progeria

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9
Q

What holds the inner membrane and outermembrane of the nucleus together?

A

LINC complex

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10
Q

What are the names of the proteins that hold together the inner membrane?

A

SUN/KASH proteins

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11
Q

What are the names of the proteins that hold together the outer membrane to the cytoskeleton

A

nesprins

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12
Q

What do nesprins do?

A
  • connect to different cytoskeleton elements ( i.e either actin, intermediate filaments or microtubules)
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13
Q

What are the 6 proteins that make up the nuclear matrix in the nucleus?

A
  • NuMa
  • Titin
  • Spectrin
  • PLF
  • Nuclear actin
  • Motor proteins
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14
Q

Role of NuMa

A

Organisation of chromatin

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15
Q

Role of titin

A

binds chromosomes and lamina

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16
Q

Role of Spectrin

A

elastic component of lamina

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17
Q

Role of PLF

A

pore linked filaments

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18
Q

Role of nuclear actin

A

short filaments or monomeric

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19
Q

Role of motor proteins

A

nuclear myosin , kinesins

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20
Q

What are chromosomes?

A

DNA - protein complex specially packaged for cell division

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21
Q

What is chromatin?

A

complex of DNA, RNA and proteins

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22
Q

What is Euchromatin

A 
“true” chromatin
• Less visible by microscopy
• Not so densely packed
• Majority of the genome (~90%)
• Localised in central part of nucleus
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23
Q

What is heterochromatin

A
  • “different” chromatin
  • Looks dark under the microscope
  • Tightly-packed condensed DNA
  • Localised around lamina and nucleoli
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24
Q

How are chromosomes arranged in the nucleus?

A

arranged discretely

25
Q

What are other names for euchromatin/heterochromatin?

A

A/B chromatin

26
Q

What are LADS?

A

Lamina - associated domains

27
Q

Where is the most little RNA production found in the nucleus?

A

n LADs (heterochromatin) than away from lamina (euchromatin)

28
Q

What molecules need to be exported out of the nucleus?

A
  • mRNA – messenger (genes)
  • rRNA – ribosomal
  • tRNA – transfer (protein synthesis)
  • Assembled ribosomal subunits
29
Q

What molecules need to be imported from the cytoplasm into the nucleus?

A
  • RNA polymerase
    • Ribosomal proteins
    • Transcription factors
    • All other structural proteins (lamins, histones, etc)
30
Q

How is the nuclear pore complex composed?

A
  • ring structure with 8 fold symmetry

- 30 different Nuclear Pore proteins ( NUPs)

31
Q

What is the central channel composed of?

A

FG*-Nups that form selective barrier to transport

32
Q

What lies on the Nuclear pore complex on the cytosolic side?

A

Fibrils

33
Q

What lies on the Nuclear pore complex on the nuclear side?

A

Nuclear basket

34
Q

What are the two types of movement through the NPC (nuclear pore complex)

A
  • passive transport

- facilitated transport

35
Q

What type of molecules can get into the nucleus via passive transport

A

small molecules and proteins

36
Q

What molecules need facilitated transport to get into the nucleus?

A

RNAs, larger proteins and macromolecular complexes

37
Q

How can facilitated transport get the energy to pump molecules into the nucleus?

A

Facilitated transport requires energy
• ATP hydrolysis for mRNA
• GTP hydrolysis for proteins, tRNA, and ribosomes

38
Q

What is the mRNP?

A

mRNA-protein complex

Includes processing, capping, splicing proteins as well as export factors

39
Q

How does the nucleus prevent the mRNP from returning to the nucleus?

A

ATP hydrolysis  release of Dbp5 in cytoplasm and mRNP remodelling prevents movement back into the nucleus

40
Q

How do nuclear import proteins, importins, transport cargo into the nucleus?

A
  • Bind cargo proteins in cytoplasm

* Interact with FG-Nups

41
Q

How is the Cargo released from the importins once in the nucleus?

A

Cargo release enabled by Ran-GTP binding to importin-b
 Conformational change that
results in complex coming apart

42
Q

What are the name of proteins which provide nuclear exportation?

A

Exportins

43
Q

how are the exporting released from the cargo in the cytoplasm

A

Ran-GTP hydrolysed to Ran-GDP in cytoplasm

conformational change that results in complex degradation

44
Q

What are GTPases?

A
  • molecular switches
  • bind to Ran, Ras, Rho, and other families
  • conformational change in the GTPasebind or unbind proteins
45
Q

What does RAN - GAP do?

A

GTP hydrolysis to GDP

46
Q

What does RAN- Geff do?

A

GTP loading after hydrolysis

47
Q

What is an NLS and an NES?

A

Nuclear localisation signal (NLS) and Nuclear export signal (NES)

48
Q

Where are NLS or NES ‘s found?

A

A nuclear localization signal or sequence (NLS) is an amino acid sequence that ‘tags’ a protein for import into the cell nucleus

49
Q

What makes up a Nuclear localisation signal?

A
  • Protein motif typically 8 amino acids long
  • Can occur anywhere in the protein
  • Many basic residues such as lysine (K), arginine (R), and proline (P)
  • Binds to importins
50
Q

What makes up an nuclear export signal?

A
  • Sequence with four hydrophobic amino acids (most often leucine, L)
  • E.g. LxxxLxxLxL, where x is any other amino acid
  • Binds to exportins
51
Q

What are the major functions of the nucleolus?

A
  • Transcription of rRNA

- Assembly of ribosomal subunits

52
Q

what is the nucleolus composed of?

A 
• Segments of 10 chromosomes encoding rRNA genes
• Proteins for processing rRNAs
• Ribsomal subunit proteins
• Small nucleolar RNA (snoRNA)
oligonucleotides that help process rRNAs
53
Q

What are other less known functions of the nucleolus?

A

Sensing and responding to stress

• Cell cycle regulationCancer

54
Q

size of canal bodies

A

0.2 – 2 mm diameter

55
Q

size of PML bodies

A

0.1 – 1 mm diameter

56
Q

size of speckles

A

20 nm – 1 mm diameter

57
Q

Function of Cajal bodies

A

RNA processing

• Genome organization (chromosome domain boundaries)

58
Q

Function of PML bodies

A
  • Often associated with Cajal bodies

* DNA repair, cell proliferation, programmed cell death

59
Q

Function of Speckles

A

Gene transcription

• mRNA processing (splicing to make various versions of genes)

Cell biology - BB10005 (17 decks)

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