Translation

Question 1

What is the primary site of translation initiation?

Answer 1

5’ G cap

Question 2

What is the secondary site of translation initiation?

Answer 2

AUG start codon and Kozak or Shine-Dalgarno sequence

Question 3

What is the purpose of the Cap binding complex in translational initiation?

Answer 3

It recruits the small subunit of the ribosome to mRNA

Question 4

How does the cap binding complex regulate translation?

Answer 4

It ensures that only mRNA’s that are capped are translated by binding to the cap and recruiting the small ribosomal subunit to the mRNA

Question 5

What are the three subunits that make up eIF4F?

Answer 5

A, G, E (A+G+E = eIF4F)

Question 6

What is the relationship between cancer cells and eIF4F?

Answer 6

Cancer cells have increased levels of eIF4F that leads to higher rates of translation

Question 7

Which subunit of eIF4F is the limiting subunit?

Answer 7

E

Question 8

Describe a weak mRNA?

Answer 8

A mRNA that is produced minimally under normal conditions and is produced en mass due to a response to a particular stimuli, these mRNA are weak and rapidly degraded

Question 9

Describe a strong mRNA.

Answer 9

Always present, regulating normal cell conditions, constantly being transcribed in significant amounts

Question 10

Define Polysome.

Answer 10

Multiple ribosomes lined up on a single mRNA translating the same protein simultaneously (direction of 5-3 and N to C)

Question 11

What is the role of a tRNA?

Answer 11

Serves as an adaptor between nucleotide sequences and amino acids

Question 12

The amino acid is bound to which end of the tRNA?

Answer 12

3’

Question 13

What is considered the second genetic code?

Answer 13

The aminoacyl tRNA synthetases are proteins that match the correct tRNA with the correct amino acid. The information and function that takes place in pairing the two together is considered the second genetic code

Question 14

How many different aminoacyl tRNA synthetases are present in a cell?

Answer 14

20

Question 15

What does charging refer to?

Answer 15

Charging is the addition of an amino acid to a tRNA through the hydrolysis of ATP. When the AA is bound to the tRNA, the tRNA is considered charged

Question 16

What is the sequence of events that leads to tRNA charging?

Answer 16

1. AA and ATP are reacted to produce an adenylated AA (AA + AMP) and PPi is released. 2. The adenylated AA binds to the tRNA releasing the AMP added in the previous step. 3. Final products are charged tRNA (tRNA + AA), AMP and PPi

Question 17

What is the function of eIF2?

Answer 17

eIF2 escorts the methionyl tRNA to the ribosome

Question 18

What is the function of eIF1 and eIF3?

Answer 18

binds the small ribosomal subunit in place and interacts with the cap binding complex to bring the ribosome to the mRNA

Question 19

What happens when AUG is recognized by the small ribosomal subunit?

Answer 19

The large ribosomal subunit combines with the small subunit

Question 20

What causes the release of initiation factors?

Answer 20

The recognition of AUG

Question 21

What is the name of the recognition sequence for Eukaryotes?

Answer 21

Kozak

Question 22

What is the name of the recognition sequence for Prokaryotes?

Answer 22

Shine - Dalgarno

Question 23

When does the large subunit join the ribosome?

Answer 23

Upon the small sub unit recognizing the start sequence

Question 24

What does polycistronic imply? Is it pro or eukaryotic

Answer 24

Prokaryotic - polycistronic means multiple start sequences are present on a single mRNA allowing for different proteins to be made from a single mRNA

Question 25

What does monocistronic imply? Is it pro or eukaryotic

Answer 25

Eukaryotic - monocistronic implies there is a single start sequence and a single protein can be made from one mRNA molecule

Question 26

What is the Poly A Binding Protein (PABP)

Answer 26

PABP binds to the Poly A tail added to the mRNA that links the tail to the head creating a loop that allows for faster subsequent rounds of translation

Question 27

Peptide Transferase is an example of a...

Answer 27

Ribozyme (it is an enzyme but not a protein, it is a mRNA molecule

Question 28

The energy molecule that powers the peptide bond formation is...

Answer 28

ATP (hydrolysis)

Question 29

What Elongation factor is responsible for translocation of the ribosome

Answer 29

EF2

Question 30

What Elongation factor brings in new charged tRNA to the A site?

Answer 30

EF1

Question 31

What is the sequence for translation WRT the ribosome during translation

Answer 31

1. EF1 brings charged tRNA to empty A site. 2. peptide bond is created between polypeptide to new AA in the A site. 3. EF2 causes ribosome to move one position down the mRNA opening up the A site again

Question 32

What causes termination?

Answer 32

Upon reaching the stop codon Release Factor binds to the A site and catalyzes the release of protein from tRNA and disassembly of the ribosome

Question 33

What protein regulates eIF4E

Answer 33

4E Binding Proteins bind eIF4E sequestering them and slowing or stopping translation from occurring. 4EBP are "anti oncogenic"

Question 34

What can cause stress response from the ER

Answer 34

``` Ca depletion Reduction of disulfide bonds Expression of mutant proteins misfiling proteins ischemia UV light exposure ```

Question 35

What does a misfolded protein cause to happen

Answer 35

1. Translation stops. Chaperone proteins come in to unfold the protein and allow it to refold correctly if possible

Question 36

If protein accumulation continues what happens to the cell?

Answer 36

Apoptosis

Question 37

What is the consequence of eIF2 being phosphorylated by PERK

Answer 37

eIF2 can no longer bring the methionyl tRNA to the ribosome

Question 38

What is the underlying cause of Walcott-Rallison Syndrome

Answer 38

Mutation and non functioning PERK gene

Question 39

What are the symptoms of Walcott Rallison Syndrome

Answer 39

Severe neonatal onset diabetes, epiphyseal dysplasia, osteoporosis and growth retardation

Question 40

How is alzheimers related to eIF2 phosphorylation

Answer 40

misfolded protein causes phosphorylation of eIF2 shutting down translation, the misfolded proteins can not be fixed which leads to continued phosphorylation of eIF2 shutting down translation in the cell for the long term

Question 41

PERK knockout models, inhibition models or over expression of phosphatases shows what promise

Answer 41

reduced severity of disease

Question 42

What effect does phosphorylation have on 4EBP

Answer 42

Phosphorylation of 4EBP causes release of eIF4E which causes increased translation

Question 43

What is the function of PERK kinase

Answer 43

PERK Kinase is activated in response to unfolded protein, PERK phosphorylated eIF2 stopping it from participate in translation initiation and translation is shut down

Question 44

How is miRNA different from siRNA, how is it similar?

Answer 44

Difference: miRNA targets the RNA induced silencing complex to repress translation; siRNA targets the RISC to degrade mRNA. Similar: Both are used to silence genes and stop expression

Question 45

miRNA vs siRNA - which is normal, which is therapuetic

Answer 45

miRNA- natural | siRNA - therapeutic