Lecture 8 Flashcards
RNA pol I makes which rRNA?
47S rRNA
RNA pol II makes what?
mRNA
RNA pol III makes what ?
5S rRNA, tRNA
mRNA transport
-Nucleus to cytoplasm
-Ran independent pathway
-Uses TAP
tRNA transport?
-Nucleus to cytoplasm
-Uses exporting-t needs Ran
rRNA transport
-Nucleus to cytoplasm
-Ran depended
Crm1 part of importin beta family
snRNA transport?
Nucleus to cytoplasm
Ran dependent
Signals needed for mRNA transport?
- 5’ cap
- Poly-A tail
- Absence of introns
Energy used to transport mRNA to cytoplasm?
-ATP
Transport factors needed for mRNA transport?
-RNA helicases
-Nucleoporins Nup98
-TAPs
Why does incompletely spliced mRNA HIV reside in the cytoplasm?
-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
What happens if we eliminate Crm1?
You will die since you ribosomes can no longer be transported from the nucleus to the cytoplasm
Stess Granules
LLPS compartments
What are stress granules composed of?
Mostly RNA bidning proteins and different types of RNA
What happens if cell stress is chronic?
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
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)
T
What generates stress granules?
-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
Why make stress granules?
-Recruit pro aptotic factors (prevent cell death)
-Protect mRNAs from degradation during stress
Where do stress granules assemble
Cytoplasm
Why is importin alpha 1 in Stress granules?
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
SGs in cancer?
Chemotherapy stresses the cnacer cells causing them to form SGs which is harmful because cell is now less likely to die
SGs in neurodegeneration?
If the granules become perisitent this can facilitate neurodegeneration
SGs and viral infections
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
Nuclear transport receptors can prevent/reduce the formation of permanent aggregates in the cell
Transportin I binds proteins and prevents them from aggregating
Peroxisome trafficking
One way can only go from cytosol into the perozisome
Peroxisome
-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
All proteins in the matrix of the peroxisome must be imported from the cytoplasm
True
T/F: folded proteins can be transported into the peroxisomal matrix
True
What does prtoein import into peroxisomal matrix require(energy)?
ATP
Peroxins
PEX genes mediate peroxisomal biogenesis and protein import
What mediated protein import into the peroxisomal matrix?
Transient translocon
Is there a permanent pore in the peroxisome transport like NPC?
No, just a translocon
Translocon contains a lot of YG domains which fill the lumen of the translocon opening
Come from PEX13
PEX5 associates with the YG domains and the cargo and then it is translocated into the matrix
PEX5 recycling
Reversible ubiquitination moves PEX5 back to cytoplasm
Translocon pore is smaller than NPC?
Ture can only fit 2nm
Mutation in PEX5
Zellweger syndrome
Causes proteins destined for the peroxisome to not be transported
Mutation in PTS sequence
mistargeting of the protein to the mitochondria
PEX5 recognizes
SKL(C-terminus sequence)
PEX7 recognizes
PTS-2(N-terminus sequence)
Compartments of mitochondria?
Outer mitochondrial membrane
Inner mitochondrial membrane
Intermembrane space
Matrix
Actins are globular protein
Yes
Treadmilling(actin)
Rate of adding and dissociating is the same. Monomers move through actin
What causes monomers to dissociate from actin?
ATP hydrolysis
Proffin
Binds actin and prevents nucleation event and filament formation
Dynamic instability of microtubules?
Microtubules shoot out from an organizing center from plus end to minus end
Beta-tubulin
Beta-tubulins bind to GTP and the GTP is hydrolyzed to conduct dynamic instability
Rate constant of NTP form is larger
Both actin and microtubules like to polymerize when bound to NTPs
When microtubules and actin are bound to GDP?
Filaments like to diassemble
ATP/GTP caps
Form when we add more ATP or GTP to the filament then we are dissociating
Loss of ATP/GTP caps
Hydrolysis becomes faster than addition of NTP and microtubules/actin quickly diassemble
Monomers can add to both the plus and minus side
Yes
