Test 3 Nucleus

Question 1

What is the organization of the nucleolus?

Answer 1

Fibrillar center: Ribosomal RNA genes located

Dense fibrillar component: Where you transcribe your ribosomal RNA

Granular Component: Where you assemble your ribosomes.

Question 2

What is the arrangement of pre-rRNA genes?

Answer 2

• They have coding (transcription unit) and spacer elements.
  
  • The transcription unit is arranged from shorter to longer RNA subunits. (Look like branches).

Question 3

rRNA processing broad strokes

Answer 3

Start with pre-rRNA and end with individual ribosomal RNA coding regions without spacers.

Question 4

When is ribosome assembled?

Answer 4

Once subunits are exported from the nucleus into the cytoplasm.

Question 5

What is the role of the nuclear lamina in the structure of the nucleus?

Answer 5

• They are intermediate filaments and make up the cytoskeleton inside the nucleus.
  
  • Lamin A shows up after cells differentiate
  • Lamin B binds to lipid groups.

Question 6

What is Farnesylation

Answer 6

• It helps lamin proteins to attach to the nuclear membrane.
  
  • Once it reaches the membrane the farnysl leaves so that the lamin protein can bind to the membrane.

Question 7

How is nuclear lamina regulated by phosphates?

Answer 7

• Lamin breaks down due to phosphorylation,
• lamin reforms after cell division and the phosphates are removed so normal structure can come back.

Question 8

What does LINC do?

Answer 8

• It connects lamina proteins to the cytoskeleton

Question 9

What is the role of LBR and emerin?

Answer 9

Connect lamina to the membrane.

Question 10

What is the structure of the nuclear pore?

Answer 10

• PAssive transport of small molecules
• Imports proteins and exports RNAs
• Basket like structure
  
  • ​Y-complex - outer ring of pore
  • FG (phenylaline and glycine) make up a net across the pore to prevent things from just coming through.

Question 11

NF-kB regulation

Answer 11

• Blocks NLS on IkB
• Singal phosphorylates the inhibitor causing NF-IkB to degrade
• Importin binds and it goes into the Nuclear porin.

Question 12

Pho4 regualtion

Answer 12

Pho4’s NLS is phosphorylated.

It is dephosphorylated and then importin can bind and bring it into the pore.

Question 13

The Nuclear Export Signal is rich in what?

Answer 13

NES is rich in leucine

Question 14

Describe ran dependent import and export.

Answer 14

• RAN binds to both GTP and GDP.
• Import Mech:
  
  • Ran-GDP binds to the Cargo protein’s NLS
    
    • inside the nucleus it is acted on by Guanine exchange factor (GEF)
  • Becomes RAN-GTP and releases cargo
• Export mech:
  
  • RAN-GTP Binds to export protein.
  • Once in the cytoplasm it is acted on by GAP
  • Becomes RAN-GDP and releases cargo.

Question 15

Ran-independent nuclear export.

Answer 15

Dbp5 hydrolyzes ATP to ADP, which causes NXF1 and NXT1 to come off of the mRNP.

Question 16

Diseases of the lamin groups are what?

Answer 16

Laminopathies

Question 17

What is Emery-Dreifuss muscular dystrophy?

Answer 17

• It is a defect in the emerin protein in the nucleus.
  
  • Emerin aids in lamin attachment to nuclear membrane.
• This occurs due to emerin possibly contributing to membrane stabilization during contractions of muscle fibers.

Question 18

What is Hutchinson-Gilford progeria?

Answer 18

• Defect in lamin A,C gene, effects site of farnysl attachment.
  
  • Farnesyl cant detach so it makes the nucleus mishapen.

causes premature aging and cardio vascular diesease.