EFFECTS OF 3'-UNTRANSLATED AND INTERGENIC REGIONS ON GENE-EXPRESSION IN TRYPANOSOMA-CRUZI

The effects of 3' untranslated regions (UTR) and intergenic regions (I NT), from various Trypanosoma cruzi stage-specific and constitutive ge nes, on the expression of the reporter firefly luciferase gene (luc), were studied using stable episomal transformation. The 3' UTR influenc ed luciferase expression by changing the steady-state level and/or the translation efficiency of luc mRNA. Glycoprotein 72 gene (gp72), glyc oprotein 85 gene (gp85) or amastin gene (ama) 3' UTR decreased the luc mRNA level 6- to 14-fold, compared to the glyceraldehyde I-phosphate dehydrogenase gene (gapdh)3' UTR, in epimastigotes. Luciferase activit y decreased in parallel with the luc mRNA level in transformants utili zing the gp85 or ama 3' UTR, whereas luc mRNA containing the gp72 3' U TR showed approximately 5-fold higher translation efficiency than luc mRNA containing a minimal 3' UTR. In amastigotes, the inhibitory effec t of the ama 3' UTR observed in other life cycle stages was abolished and luciferase expression was stimulated 16-fold. The overall stage-sp ecific difference mediated by the ama 3' UTR, between epimastigotes an d amastigotes, was approximately 100-fold. INT, which was expected to influence polyadenylation efficiency, of gapdh, gp72, or heat shock pr otein 60 gene inserted after gapdh 3' UTR increased luc mRNA 2- to 8-f old, whereas gp85 INT slightly decreased luc mRNA. By separating effec ts attributable to the 3' UTR and INT, this study shows the effects of 3' UTR on RNA levels and translational efficiency in T, cruzi.