Exam 1 - Translation

Question 1

what is the quality control #1 for translation initiation

Answer 1

presence of a 5’ and 3’ poly a tail

Question 2

What are the 5 steps of translation initiation?

Answer 2

1 - Small subunit binds to mRNA first
2 - tRNAi-MET binds to P site
3 - small subunit + tRNA-MET scan 5’UTR until finds AUG
4 - eLF’s dissociate when large subunit binds
5 - ribosome recycling

Question 3

what are the 5 steps of translation elongation?

Answer 3

1 - aa-tRNA enter A site
2 - peptide bond forms
3 - large subunit slides (changing tRNA from A –> P —> E
4 - small subunit slides down the mRNA and tRNA is ejected
5 - repeat

Question 4

what are the 2 steps os translation termination?

Answer 4

1 - release factors (eIF)
- shaped like a tRNA but does not have an amino acid

2 - eRF 1 works with eRF3
- eRF3 is a GTPase
- eRF1 interactions with stop codon

Question 5

eIF1/ A

Answer 5

blocks tRNAi-MET from entering A/E sites

Question 6

eIF2

Answer 6

loads tRNAi-MET to the P site

Question 7

eIF3

Answer 7

WORKHORSE. loads small subunit onto mRNA, recruits other eIF’s, promotes scanning, prevents large subunit from binding

Question 8

eIF4F/ eLF4E/ A/ G

Answer 8

binds mRNA 5’cap

Question 9

eIF5

Answer 9

releases other eIF’s to allow large subunit binding after AUG is found

important in starting initiation for translation

Question 10

eIF6

Answer 10

prevents large subunit binding

could cause issues if have too much

Question 11

What are the 3 elongation factors for eukaryotes?

Answer 11

1 - eEF1A: recruits aa-tRNA to A site (a G protein)
2 - eEF1B: regenerates up (a GEF)
3 - eEF2: ribosome translocation (a G protein)

Question 12

Elongation error occurs most when ______ and when the elongation factors speed up translation _______ fidelity.

Answer 12

1 - slower speeds
2 - increases

Question 13

what is nonsense mediated decay (NMD)

Answer 13

• detection and degradation of mRNA with premature stop codons
• proteins
  a) UPF: helicase removes RNA hairpins
  b) SMG: kinase phosphorylates UPF1
  c) eRFs: end translations
• triggers
  a) incorrect splicing retains exon junction proteins
  b) 3’UTR too long

Question 14

How does UPR control misfolded proteins?

Answer 14

1 - chaperones (try again)
2 - proteasomes (degradation)
3 - apoptosis (evade detection)
4 - stop making protein

Question 15

what protein coats the poly a tail?

Answer 15

PABP

Question 16

which protein adds adenines to the tail?

Answer 16

PAP

Question 17

which RNA would be best used to inhibit translation without degrading the mRNA of a specific gene

a - snRNA
b - lncRNA
c - piRNA
d - siRNA
e - miRNA

Answer 17

e - miRNA

Question 18

which of the following translation initiation factor prevents the large subunit from binding

a - eIF3 and eIF6
b - eIF1 and eIF6
c - eIF1 and eIF2
d - eIF5 and eIF4F
e - eIF4F and eIF3

Answer 18

a

Question 19

for translation initiation the _______ binds first and during translation elongation the _______ slides first.

Answer 19

1 - small
2 - large