TRANSLATIONAL ACTIVATION AND CYTOPLASMIC POLYADENYLATION OF FGF RECEPTOR-1 ARE INDEPENDENTLY REGULATED DURING XENOPUS OOCYTE MATURATION

FGF signaling is critical for establishing the Xenopus laevis embryoni c body plan and requires the expression of functional EGF receptor dur ing early embryogenesis. FGF receptor-1 (XFGFR) maternal mRNA is prese nt in immature oocytes, but the protein is not expressed until oocyte maturation. In this report we demonstrate that endogenous XFGFR transl ation begins just prior to germinal vesicle breakdown and that transla tion depends on completion of earlier meiotic events. We show that the previously identified XFGFR 3'UTR translation inhibitory element (TIE ), which is necessary and sufficient for repressing translation in the immature oocyte, also regulates the onset of translation during oocyt e maturation. In addition we demonstrate that cytoplasmic polyadenylat ion of XFGFR RNA is regulated independently of TIE-mediated translatio n and is not sufficient to activate the translation of XFGFR. These ex periments reveal that polyadenylation and translational activation are separable events in this mRNA, each of which is timed and regulated i ndependently. (C) 1998 Academic Press.