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. Author manuscript; available in PMC: 2016 Dec 13.
Published in final edited form as: Neuron. 2009 Jan 15;61(1):10–26. doi: 10.1016/j.neuron.2008.10.055

Figure 1. Molecular Model for ATF4 mRNA Translational Control.

Figure 1

The ATF4 mRNA (straight line), harbors uORFs 1 and 2 (green boxes). Upon translation of uORF1, the 80S ribosome dissociates and the 40S ribosomal subunit remains attached to the mRNA and resumes scanning in a 5′ to 3′ direction.

(A) Under normal conditions, there is a sufficient supply of ternary complex (eIF2-Met-tRNAiMet-GTP), which rapidly associate with the 40S ribosomal subunit. This enables the 40S subunit to reinitiate translation at the AUG of uORF2. The 80S ribosome dissociates after terminating at uORF2. As the 40S ribosomal subunit cannot scan backward, the AUG codon of ATF4 cannot be translated.

(B) Under conditions in which eIF2α is phosphorylated, the amount of ternary complex is reduced. Thus, a significant portion of scanning 40S ribosomal subunits scan pass the AUG of uORF2 and initiate at the AUG of ATF4.