Exam 1 - Translation Flashcards
what is the quality control #1 for translation initiation
presence of a 5’ and 3’ poly a tail
What are the 5 steps of translation initiation?
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
what are the 5 steps of translation elongation?
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
what are the 2 steps os translation termination?
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
eIF1/ A
blocks tRNAi-MET from entering A/E sites
eIF2
loads tRNAi-MET to the P site
eIF3
WORKHORSE. loads small subunit onto mRNA, recruits other eIF’s, promotes scanning, prevents large subunit from binding
eIF4F/ eLF4E/ A/ G
binds mRNA 5’cap
eIF5
releases other eIF’s to allow large subunit binding after AUG is found
important in starting initiation for translation
eIF6
prevents large subunit binding
could cause issues if have too much
What are the 3 elongation factors for eukaryotes?
1 - eEF1A: recruits aa-tRNA to A site (a G protein)
2 - eEF1B: regenerates up (a GEF)
3 - eEF2: ribosome translocation (a G protein)
Elongation error occurs most when ______ and when the elongation factors speed up translation _______ fidelity.
1 - slower speeds
2 - increases
what is nonsense mediated decay (NMD)
- 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
How does UPR control misfolded proteins?
1 - chaperones (try again)
2 - proteasomes (degradation)
3 - apoptosis (evade detection)
4 - stop making protein
what protein coats the poly a tail?
PABP
which protein adds adenines to the tail?
PAP
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
e - miRNA
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
a
for translation initiation the _______ binds first and during translation elongation the _______ slides first.
1 - small
2 - large
