Lecture 8

Question 1

RNA pol I makes which rRNA?

Answer 1

47S rRNA

Question 2

RNA pol II makes what?

Answer 2

mRNA

Question 3

RNA pol III makes what ?

Answer 3

5S rRNA, tRNA

Question 4

mRNA transport

Answer 4

-Nucleus to cytoplasm
-Ran independent pathway
-Uses TAP

Question 5

tRNA transport?

Answer 5

-Nucleus to cytoplasm
-Uses exporting-t needs Ran

Question 6

rRNA transport

Answer 6

-Nucleus to cytoplasm
-Ran depended
Crm1 part of importin beta family

Question 7

snRNA transport?

Answer 7

Nucleus to cytoplasm
Ran dependent

Question 8

Signals needed for mRNA transport?

Answer 8

1. 5’ cap
2. Poly-A tail
3. Absence of introns

Question 9

Energy used to transport mRNA to cytoplasm?

Answer 9

-ATP

Question 10

Transport factors needed for mRNA transport?

Answer 10

-RNA helicases
-Nucleoporins Nup98
-TAPs

Question 11

Why does incompletely spliced mRNA HIV reside in the cytoplasm?

Answer 11

-mRNA comes from the virus
-Have Rev response element which is recognized by Rev when this binds the NES is recognized by Crm1 and it allows the incompletely spliced mRNA to get from nucleus into the cytoplasmW

Question 12

What happens if we eliminate Crm1?

Answer 12

You will die since you ribosomes can no longer be transported from the nucleus to the cytoplasm

Question 13

Stess Granules

Answer 13

LLPS compartments

Question 14

What are stress granules composed of?

Answer 14

Mostly RNA bidning proteins and different types of RNA

Question 15

What happens if cell stress is chronic?

Answer 15

Stress granules will transition to a more gel-like consistency which cannot be disassembled
Wosrt case: fibrils will be generated which are permanent and damaging to the cell

Question 16

T/F:The formation of stress granules is stress dependent and transient (get rid of the stress then you get rid of the stress granules)

Answer 16

T

Question 17

What generates stress granules?

Answer 17

-Oxidative stress (hypoxia, kidney will generate stress granules), also seen after heart attacks or strokes)
Temperature stress (most relevant to humans (fever))
Changes in pH
Changes in salt

Question 18

Why make stress granules?

Answer 18

-Recruit pro aptotic factors (prevent cell death)
-Protect mRNAs from degradation during stress

Question 19

Where do stress granules assemble

Answer 19

Cytoplasm

Question 20

Why is importin alpha 1 in Stress granules?

Answer 20

Helps assemble full sized SGs
Without importin-alpha 1 cells make smaller SGs and the cells are more prone to death when you stress them

Question 21

SGs in cancer?

Answer 21

Chemotherapy stresses the cnacer cells causing them to form SGs which is harmful because cell is now less likely to die

Question 22

SGs in neurodegeneration?

Answer 22

If the granules become perisitent this can facilitate neurodegeneration

Question 23

SGs and viral infections

Answer 23

Granules are often generated for many virus infections this can be bad because viruses such as HIV interfere with the proper formation of SGs this makes the cell more prone to cell death and leads to increased infectivity

Question 24

Nuclear transport receptors can prevent/reduce the formation of permanent aggregates in the cell

Answer 24

Transportin I binds proteins and prevents them from aggregating

Question 25

Peroxisome trafficking

Answer 25

One way can only go from cytosol into the perozisome

Question 26

Peroxisome

Answer 26

-A bag of enzymes which are approximately 0.2 to 1 micron in diameter Have a single membrane and a single matrix Important for many detoxification reactions Important for the degradation of long chain fatty acids Important for the generation of myelin

Question 27

All proteins in the matrix of the peroxisome must be imported from the cytoplasm

Answer 27

True

Question 28

T/F: folded proteins can be transported into the peroxisomal matrix

Answer 28

True

Question 29

What does prtoein import into peroxisomal matrix require(energy)?

Answer 29

ATP

Question 30

Peroxins

Answer 30

PEX genes mediate peroxisomal biogenesis and protein import

Question 31

What mediated protein import into the peroxisomal matrix?

Answer 31

Transient translocon

Question 32

Is there a permanent pore in the peroxisome transport like NPC?

Answer 32

No, just a translocon

Question 33

Translocon contains a lot of YG domains which fill the lumen of the translocon opening

Answer 33

Come from PEX13 PEX5 associates with the YG domains and the cargo and then it is translocated into the matrix

Question 34

PEX5 recycling

Answer 34

Reversible ubiquitination moves PEX5 back to cytoplasm

Question 35

Translocon pore is smaller than NPC?

Answer 35

Ture can only fit 2nm

Question 36

Mutation in PEX5

Answer 36

Zellweger syndrome Causes proteins destined for the peroxisome to not be transported

Question 37

Mutation in PTS sequence

Answer 37

mistargeting of the protein to the mitochondria

Question 38

PEX5 recognizes

Answer 38

SKL(C-terminus sequence)

Question 39

PEX7 recognizes

Answer 39

PTS-2(N-terminus sequence)

Question 40

Compartments of mitochondria?

Answer 40

Outer mitochondrial membrane Inner mitochondrial membrane Intermembrane space Matrix

Question 41

Actins are globular protein

Answer 41

Yes

Question 42

Treadmilling(actin)

Answer 42

Rate of adding and dissociating is the same. Monomers move through actin

Question 43

What causes monomers to dissociate from actin?

Answer 43

ATP hydrolysis

Question 44

Proffin

Answer 44

Binds actin and prevents nucleation event and filament formation

Question 45

Dynamic instability of microtubules?

Answer 45

Microtubules shoot out from an organizing center from plus end to minus end

Question 46

Beta-tubulin

Answer 46

Beta-tubulins bind to GTP and the GTP is hydrolyzed to conduct dynamic instability

Question 47

Rate constant of NTP form is larger

Answer 47

Both actin and microtubules like to polymerize when bound to NTPs

Question 48

When microtubules and actin are bound to GDP?

Answer 48

Filaments like to diassemble

Question 49

ATP/GTP caps

Answer 49

Form when we add more ATP or GTP to the filament then we are dissociating

Question 50

Loss of ATP/GTP caps

Answer 50

Hydrolysis becomes faster than addition of NTP and microtubules/actin quickly diassemble

Question 51

Monomers can add to both the plus and minus side

Answer 51

Yes