Figure 3 - A model for the regulation of amastin gene expression in T. cruzi. The amastin/tuzin gene cluster is shown, with dark and gray boxes representing copies of tuzin and amastin genes, respectively. Intergenic regions are shown as thin lines (The diagram including the restriction sites was modeled after Teixeira et al. (43)). Polycistronic transcription, which occurs at the same rates in amastigotes and epimastigotes, generates a pre-mRNA (wavy lanes) that needs to be processed in order to produce mature mRNA encoding amastin (gray box) and tuzin (dark box) proteins. The differential accumulation of these mRNAs in the two forms of the parasite's life cycle may be dependent upon at least two factors: higher efficiency of amastin mRNA processing and increased stability of the mRNA in amastigotes. An RNA-binding protein, which is more abundant in amastigotes, is proposed to be involved in the regulatory pathway through specific binding at the 3'UTR of amastin mRNA (gray line).