Translation and its regulation (lect 9)

Question 1

Which initiation factor binds to tRNA to form the ternary complex?

Answer 1

eIF2

Question 2

Which initiation factor binds to mRNA to activate it?

Answer 2

eIF4F

Question 3

How does eIF4F activate mRNA?

Answer 3

acts as helicase, unwinds it from end proximal to cap

Question 4

Which initiation factor is 60S binding dependent on?

Answer 4

eIF5b-GTP
(GTP hydrolysed to GDP when 60S binds)

Question 5

Regulation of ATF4 (stress genes tf) translation

Answer 5

Stress:
high eIF2α-P, low eIF2α-GTP
-delayed ternary complex formation
-uORF1 translated but inhibitory uORF2 is not, meaning ATF4 can be translated

Non-stress:
low eIF2α-P, high eIF2α-GTP
-ternary complex formation as normal
-uORF1 and inhibitory uORF2 translated

Question 6

Regulation of APAF1 (stress response protein) translation

Answer 6

UNR and NPTB (trans-acting factors) remodel APAF1 mRNA to create internal ribosome entry site for 40S to bind to