Regions in the 3' untranslated region confer stage-specific expression to the Leishmania mexicana a600-4 gene.

Protozoan parasites of the genus Leishmania have a digenetic lifecycle, alternating between the promastigote and amastigote stages. The extracellular promastigote resides within a sandfly vector, while the obligate intracellular amastigote stage replicates in the phagolysosome of mammalian host macrophages. Adaptation to and survival within these vastly differently environments is accompanied by differential expression of a subset of genes, which is regulated post-transcriptionally via cis-acting elements in 3' untranslated region (3'UTR) or intercistronic sequences. It was reported previously that Leishmania mexicana A600-4 mRNA transcript abundance was eight-fold higher in the amastigotes. In this study, chimeric luciferase:A600-4 3'UTR reporter constructs were integrated at the A600 chromosome locus to identify regulatory regions of the A600-4 3'UTR sequence. Evidence is provided for distinct 3'UTR elements that function to stabilize the A600-4 mRNA transcript in the amastigote stage and to regulate translation efficiency, respectively.