CYTOPLASMIC 3'-POLY(A) ADDITION INDUCES 5'-CAP RIBOSE METHYLATION - IMPLICATIONS FOR TRANSLATIONAL CONTROL OF MATERNAL MESSENGER-RNA

During the early development of many animal species, the expression of new genetic information is governed by selective translation of store d maternal mRNAs. In many cases, this translational activation require s cytoplasmic poly(A) elongation. However, how this modification at th e 3' end of an mRNA stimulates translation from the 5' end is unknown. Here we show that cytoplasmic polyadenylation stimulates cap ribose m ethylation during progesterone-induced oocyte maturation in Xenopus la evis. Translational recruitment of a chimeric reporter mRNA that is co ntrolled by cytoplasmic polyadenylation coincides temporally with cap ribose methylation during this period. In addition, the inhibition of cap ribose methylation by S-isobutyladenosine significantly reduces tr anslational activation of a reporter mRNA without affecting the increa se of general protein synthesis or polyadenylation during maturation. These results provide evidence for a functional interaction between th e termini of an mRNA molecule and suggest that 2'-O-ribose cap methyla tion mediates the translational recruitment of maternal mRNA.