Stimulation of translation and cytoplasmic polyadenylation by the Xenopus c-mycI 3'-untranslated region.
Expression of messenger RNA (mRNA) in both embryonic and adult cells may be profoundly influenced by untranslated sequences in the 3'-end. Elements in the 3'-untranslated regions (UTRs) of messengers are known to influence messenger stability, polyadenylation, and translation. We have examined the effects of the 3'-UTR of Xenopus laevis c-mycI (either alone or in combination with the 5'-first exon) on the expression of a chloramphenicol acetyltransferase (CAT) reporter in Xenopus embryos. The Xenopus c-mycI 3'-UTR enhanced messenger translation independent of the 5'-UTR. RNase H analysis indicated that the Xenopus c-mycI 3'-UTR can promote the cytoplasmic polyadenylation of CAT mRNA in embryos. The result suggests that the post-fertilization enhancement of translation caused by the c-mycI 3'-UTR may be a consequence of cytoplasmic polyadenylation. A uridine (U)-rich sequence in the Xenopus c-mycI 3'-UTR that may be responsible for polyadenylation is similar to an element that destabilizes mammalian c-myc transcripts. We discuss the possibility that U-rich sequences may play a dual role by destabilizing growth-related transcripts in adult cells and stimulating their polyadenylation during development, and we propose that a switch in the role of such sequences in adult cells could lead to stabilization of these messengers, increased translation, and abnormal growth control.
Fraser
S D
SD
Department of Biological Sciences, University of Calgary, Alberta, Canada.
Browder
L W
LW
D000818:Animals; D001483:Base Sequence; D003593:Cytoplasm / Q000378:metabolism; D005091:Exons; D016259:Genes, myc; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism*; D014982:Xenopus laevis
D012333:RNA, Messenger