Lectures 9-10: Post-transcriptional control of gene expression 2

Question 1

which enzymes catalyse tRNA charging?

Answer 1

aminoacyl-tRNA synthetases

Question 2

eukaryotic translation depends on what, located on the mRNA?

Answer 2

the 5’ cap

Question 3

the most frequently found sequence around the AUG in eukaryotic mRNA is called the …………… sequence

Answer 3

kozak consensus

Question 4

which proteins are needed for mRNA circularisation?

Answer 4

eIF4E, G, PAB

Question 5

which cap does eIF4E bind to?

Answer 5

m7G

Question 6

which protein binds to eIF4G?

Answer 6

PAB protein

Question 7

what is needed for 43S association?

Answer 7

eIF3 and eIF4G interactions and RNA unwinding

Question 8

name the GTPase that is required for the subunit binding of AUG and Met

Answer 8

eIF5B

Question 9

as part of the initiation complex, what is recruited to the cap and then scans along until it reaches the AUG?

Answer 9

small ribosomal subunit

Question 10

what happens to eIF2B in responses to stress such as viral infection?

Answer 10

it is down regulated/ phosphorylated so therefore translation initiation of mRNA = reduced

Question 11

eIF2 has 3 subunits. what are they?

Answer 11

alpha, beta, gamma

Question 12

eIF2 alpha is phosphorylated on which Ser?

Answer 12

Ser51

Question 13

eIF2 beta binds to which 2 elongation initiation factors?

Answer 13

eIF2B, eIF5

Question 14

eIF2 gamma is associated with what?

Answer 14

Met-tRNA

Question 15

Name the 4 eIF2 kinases which are all stresses

what happens to these kinases under stimulatory conditions?

Answer 15

PKR (viral infection)
PERK (endoplasm stress)
GCN2 (amino acid stress)
HRI (globin stress)

they dimerise, then autophosphorylate and act on substrate

Question 16

which eIF2 kinase expression increases when cells are exposed to interferons?

Answer 16

PKR

Question 17

Where are iron response elements found in mRNA?

what binds these elements?

Answer 17

in the 5’ or 3’ UTRs (untranslated regions)

bound by iron regulatory proteins 1 and 2

Question 18

which other form can IRP1 take as it is a bifunctional protein?

what is the function?

Answer 18

c - aconitase = interconverts citrate and isocitrate

Question 19

why does RNA degrade?

Answer 19

damaged mRNA, incorrectly transcribed mRNA

Question 20

in the mammary gland, what happens to the half life of mRNA in response to prolactin production?

what happens to the length of the polyA tail

Answer 20

half life increases

length of tail increases

Question 21

which 3 enzymes initiate the breakdown of the RNA?

Answer 21

decapping enzymes
endonucleases
deadenylases

Question 22

in the second phase of mRNA degredation, what acts as a 3’ to 5’ exonuclease?

Answer 22

the exosome

Question 23

in the second phase of mRNA degredation, what acts as a 5’ to 3’ exonuclease?

Answer 23

XRN1

Question 24

what is deadenylation dependent decay?

Answer 24

a mechanism where all mRNAs lose their polyA tails

Question 25

PMR1 cleaves albumin mRNA by which type of decay?

Answer 25

deadenylation INDEPENDENT

Question 26

which type of decay removes mRNA with premature stop codons?

Answer 26

nonsense mediated decay

Question 27

errors in transcription, splicing, editing, polyadenylation result in the formation of what?

Answer 27

premature stop codons

Question 28

after mRNA has been de-circularised in mRNA decay, what happens?

Answer 28

the cap or polyA tail is removed

Question 29

siRNA and miRNA are both ……. nucleotides long

Answer 29

21-23

Question 30

which mRNA is thought to be mainly a viral defense mechanism, leading to the degredation of the target RNA?

Answer 30

siRNA

Question 31

which mRNA is thought to be a key gene regulatory mechanism in the cell, leading to a block in translation

Answer 31

miRNA

Question 32

in embryonic development, 3’ UTRs get …….

Answer 32

longer

Question 33

in proliferating cells, compared to embryonic cells, UTRs are……

Answer 33

shorter