Abstract
In recent years, our thinking of how the initiation of protein synthesis occurs has changed dramatically. Initiation was thought to involve only events occurring at or near the 5′-cap structure, which serves as the binding site for the cap-binding complex, a group of translation initiation factors (eIFs) that facilitate the binding of the 40 S ribosomal subunit to an mRNA. Because the poly(A)-binding protein (PABP) binds the poly(A) tail present at the 3′-terminus of an mRNA, it was long thought to play no role in translation initiation. In this review, I present evidence from my laboratory that has contributed to the paradigm shift in how we think of mRNAs during translation. The depiction of mRNAs as straight molecules in which the poly(A) tail is far from events occurring at the 5′-end has now been replaced by the concept of a circular mRNA where the interaction between PABP and the cap-binding complex bridges the termini of an mRNA and promotes translation initiation. The research from my laboratory supports the new paradigm that translation of most mRNAs requires a functional and physical interaction between the termini of an mRNA.
Highlights
Our understanding of how mRNAs are translated into proteins has undergone a paradigm shift in recent years
Only a single interaction domain for poly(A)-binding protein (PABP) has been reported in animal and yeast eIF4G [27,28,29,30,31], we discovered that PABP binds to two distinct sites within plant eIF4G [36]
Because the binding sites for eIF4B and PABP partially overlap with the eIF4A binding domain in the HEAT-1 domain of eIF4G, we investigated whether they would compete with eIF4A in binding eIF4G
Summary
Our understanding of how mRNAs are translated into proteins has undergone a paradigm shift in recent years Prior to this shift, a translating mRNA undergoing translation was thought of as a straight molecule and protein synthesis was considered a linear process that encompassed three phases. A translating mRNA undergoing translation was thought of as a straight molecule and protein synthesis was considered a linear process that encompassed three phases In this prior view, the first phase, that is, translation initiation, begins with events that only involve the 5-end of an mRNA in which the subunits of a ribosome are recruited and assembled at the initiation codon and conclude with the synthesis of the first peptide bond (Figure 1). The similarities and differences in the interactions of the machinery involved in ribosome recruitment in plants and those of other eukaryotes will be be discussed
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