Fig. 7

Model for differential eIF4F associations during translation initiation. Diagram depicts three different states of closed-loop mRNA complex. Bottom: State 1: a non-initiating mRNA. Top left: State 2: a 48S bound complex with contacts between eIF4G and recruited 43S factors during which scanning occurs. Top right: State 3: a post-AUG recognition complex undergoing 60S joining where initiation factors including eIF2-GDP are released. Actively initiating mRNAs likely cycle between the conformations 2 and 3 (grey arrows), correlating with low eIF4F affinity or recovery. mRNAs initiating rapidly under optimal growth conditions, but sensitive to stress transition to a conformation where eIF4F becomes more stably associated and TE lowered: red arrow to state 1. Other mRNAs have high affinity for 4 F and are initiated less frequently (state 1), but can be activated to recruit more ribosomes following stress, entering a dynamic state where 4 F affinity is lowered: green arrow to state 2