Biology 3597A/B Lecture Notes - Lecture 20: Eif2, Eif2B, Ribosome
25 Jan 2020
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Review: what is required for translation: mrna, ribosome. A classic example of both levels of control occurs during global translational repression in stress response. Phosphorylation of eif2: cells spend a lot of resources on stress response. Figure (below) shows the steps of translation initiation. Hypoxia, viral infection, amino acid starvation, heat shock etc. trigger the phosphorylation of the. Eif2 phosphorylation leads to inhibition of translation by blocking ternary complex formation. Inability to form the ternary complex results in inhibition of protein synthesis: a second subset of mrnas show an increased level of translation in these conditions, ex. Gcn4 is more actively translated during stressful conditions. Gcn4 gene in yeast has 4 upstream open reading frames (uorfs) When the ternary complex is plentiful, uorfs 2-4 can be translated, but the 40s ribosome subunit (orange egg in diagram below) cannot continue scanning never makes it to aug5. During stress, ternary complexes pass junk uorfs and go to the protein-coding start codon.
