Insights from a Paradigm Shift: How the Poly(A)-Binding Protein Brings Translating mRNAs Full Circle

Figure 1

Overview of the three steps during protein synthesis in eukaryotes. During translation initiation, a 40 S subunit is recruited at the 5′-cap through the interaction between eIF3 and eIF4G, the large subunit of the eIF4F complex that is bound to the 5′-cap through the eIF4E subunit. Secondary structure in the 5′-UTR is removed through the ATP-dependent helicase activity of eIF4A which is assisted by eIF4B. The 40 S subunit then scans down the 5′-UTR to locate the first AUG in a good context at which point the 60 S subunit joins. Protein synthesis begins with the formation of the first peptide bond at which point the initiation phase ends and the elongation phase begins until the 80 S ribosome reaches a termination codon at which point translation terminates releasing the nascent peptide. Not all initiation factors involved in translation initiation are shown and the role of PABP in translation initiation is not depicted.