Lecture 16 - Translation of RNA to Protein Regulation

Question 1

Describe eIF2

Answer 1

eIF2 Delivers Met-tRNAiMet to ribosome as “Ternary complex” with GTP

eIF2 has 3 subunits (a, b, g) & GTPase activity

Question 2

Describe how eukaryotic mRNA are circularised

Answer 2

Poly(A)-binding protein (PABP) bound to 3’ end of mRNA can interact with eIF4G at 5’-end to bring ends together
Circularisation of mRNA facilitates inhibition of eIF4 by miRNAs bound to 3’-UTR
Circularisation of mRNA also facilitates recycling of ribosomes

Question 3

What are polysome profiles?

Answer 3

Polysome profiles are produced by centrifugation of cytoplasmic extracts through sucrose gradients
mRNAs bound by many ribosomes sediment faster than mRNAs with few ribosomes bound
Use Northern blots or RT-PCR to determine which fractions contain a particular mRNA
Highly expressed mRNAs may be translated by many ribosomes simultaneously (found in Fraction 1)