CIRCULARIZATION OF MESSENGER-RNA BY EUKARYOTIC TRANSLATION INITIATION-FACTORS

Communication between the 5' cap structure and 3' poly(A) tail of euka ryotic mRNA results in the synergistic enhancement of translation. The cap and poly(A) tail binding proteins, elF4E and Pab1p, mediate this effect in the yeast S. cerevisiae through their interactions with diff erent parts of the translation factor elF4G. Here, we demonstrate the reconstitution of an elF4E/elF4G/Pab1p complex with recombinant protei ns, and show by atomic force microscopy that the complex can circulari ze capped, polyadenylated RNA. Our results suggest that formation of c ircular mRNA by translation factors could contribute to the control of mRNA expression in the eukaryotic cell.