Effects of cyclin A2 noncoding regions on reporter gene translation during early development of Xenopus laevis.

The repression of translation of Xenopus cyclin A2 transcripts during early development was examined by analyzing the effects of cyclin A2 noncoding regions using a CAT reporter system. On their own, the 5' and 3' UTRs (untranslated regions) were unable to inhibit reporter translation until approximately the time of the midblastula transition. Transcripts containing the 3' UTR were polyadenylated after fertilization and the midblastula transition. When both noncoding regions flanked a CAT reporter gene, translation was repressed at all stages of development examined in spite of their polyadenylation after fertilization. From these data, we conclude that the 5' and 3' UTRs interact synergically to prevent translation during early development and that the poly(A) tail is insufficient to promote their translation.