Lectures 9-10: Post-transcriptional control of gene expression 2 Flashcards
which enzymes catalyse tRNA charging?
aminoacyl-tRNA synthetases
eukaryotic translation depends on what, located on the mRNA?
the 5’ cap
the most frequently found sequence around the AUG in eukaryotic mRNA is called the …………… sequence
kozak consensus
which proteins are needed for mRNA circularisation?
eIF4E, G, PAB
which cap does eIF4E bind to?
m7G
which protein binds to eIF4G?
PAB protein
what is needed for 43S association?
eIF3 and eIF4G interactions and RNA unwinding
name the GTPase that is required for the subunit binding of AUG and Met
eIF5B
as part of the initiation complex, what is recruited to the cap and then scans along until it reaches the AUG?
small ribosomal subunit
what happens to eIF2B in responses to stress such as viral infection?
it is down regulated/ phosphorylated so therefore translation initiation of mRNA = reduced
eIF2 has 3 subunits. what are they?
alpha, beta, gamma
eIF2 alpha is phosphorylated on which Ser?
Ser51
eIF2 beta binds to which 2 elongation initiation factors?
eIF2B, eIF5
eIF2 gamma is associated with what?
Met-tRNA
Name the 4 eIF2 kinases which are all stresses
what happens to these kinases under stimulatory conditions?
PKR (viral infection)
PERK (endoplasm stress)
GCN2 (amino acid stress)
HRI (globin stress)
they dimerise, then autophosphorylate and act on substrate
which eIF2 kinase expression increases when cells are exposed to interferons?
PKR
Where are iron response elements found in mRNA?
what binds these elements?
in the 5’ or 3’ UTRs (untranslated regions)
bound by iron regulatory proteins 1 and 2
which other form can IRP1 take as it is a bifunctional protein?
what is the function?
c - aconitase = interconverts citrate and isocitrate
why does RNA degrade?
damaged mRNA, incorrectly transcribed mRNA
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
half life increases
length of tail increases
which 3 enzymes initiate the breakdown of the RNA?
decapping enzymes
endonucleases
deadenylases
in the second phase of mRNA degredation, what acts as a 3’ to 5’ exonuclease?
the exosome
in the second phase of mRNA degredation, what acts as a 5’ to 3’ exonuclease?
XRN1
what is deadenylation dependent decay?
a mechanism where all mRNAs lose their polyA tails
