Control of translation i

jambomber's version from 2015-05-20 18:41

Section 1

Question Answer
Why is eIF3 so ciritcal in initiation?It coordianetly binds 40S prevents 60S binding, stablises 40S TC interactions and promotes mRNA binding
What happens when the initiation codon is recognised?eIF1 is released, enabling the release of Pi from TC and causing a swith to the latch conformation- preventing scanning
How many polypeptides in eIF36 in yeast vs 13 in mammals
What is the multifactor complex?A complex between EIF 3 1 2 and 5 in yeast. Good evidence for 1+5 interacting w/ 3
Where does eIF3 bind?Back- ie solvent dace of 40S sub unit
What links RNA to ribosomeRNA- PAB+ EIF4E-(EIF4F)- EIF3-40S
What residues in eIF4E regoniss the cap?Two tryptophans W56+102 sandwich Met cap
How does eIF4G influence eIF4Es activityBinds convex site and causes a conf change which increases affinity of E for cap
Tell me about eIF4A?ATP dep, DEAD box member, weak and non processive- req eIF4B stimulation, Unwinds bidirectionally, Cycles through 4F in ATP dep manner
How do we know that eIF4F complex is the main unwinder?Dominant negative RQ eIF4A which cannot hydrolyse ATP is a potent trans inhibitor- suggests working as a complex component
What is the evidence that cap proximal 2 structures necessitates unwidning?Unstrcuted CAA*19 5UTR can be recog by 40S sub unit
What role does eIF5B serve?Ribosome dependant GTPase which catalyses sub unit joining and causes other IFs to leave.

Section 2

Question Answer
What is the evidence for the Scanning model?1) 70% of mRNAs use first AUG 2) Insertion of an upstream site shifts where init ocrus 3) Decapping reduces effiency 4) No 40S binidng to cicularised mRNAs
What is the optimal sequence for selecting a AUG ?A/GnnAUGG A/G and G are critical. Mutate upstream AUGs in sub optimal context to optimal seq- elevated freq init.
How can a suboptimal sequence be favoured?If a downstream secondary strucutre is sufficiently clos to induce ribosomal pausing
What reasons does translation occur at downstream AUFs1) Suboptimal context 2) 1st AUG too close to Cap <10nts 3) If it is followed by a short uORF
What influences a secondary structures influence on translation?1) Location- proximity to 5' stronger 2) GC content 3) Hairpin length