Circularization of mRNA by eukaryotic translation initiation factors.

Communication between the 5' cap structure and 3' poly(A) tail of eukaryotic mRNA results in the synergistic enhancement of translation. The cap and poly(A) tail binding proteins, eIF4E and Pab1p, mediate this effect in the yeast S. cerevisiae through their interactions with different parts of the translation factor eIF4G. Here, we demonstrate the reconstitution of an eIF4E/eIF4G/Pab1p complex with recombinant proteins, and show by atomic force microscopy that the complex can circularize capped, polyadenylated RNA. Our results suggest that formation of circular mRNA by translation factors could contribute to the control of mRNA expression in the eukaryotic cell.

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