Trypanosoma cruzi: Modulation of HSP70 mRNA stability by untranslated regions during heat shock

Gene regulation in trypanosomatids occurs mainly by post-transcriptional mechanisms modulating mRNA stability and translation. We have investigated heat shock protein (HSP) 70 gene regulation in Trypanosoma cruzi, the causal agent of Chagas' disease. The HSP70 mRNA's half-life increases after heat shock, and the stabilization is dependent on protein synthesis. In a cell-free RNA decay assay, a U-rich region in the 3′ untranslated region (UTR) is a target for degradation, which is reduced when in the presence of protein extracts from heat shocked cells. In a transfected reporter gene assay, both the 5′- and 3′-UTRs confer temperature-dependent regulation. Both UTRs must be present to increase mRNA stability at 37 °C, indicating that the 5′- and 3′-UTRs act cooperatively to stabilize HSP70 mRNA during heat shock. We conclude that HSP70 5′- and 3′-UTRs regulate mRNA stability during heat shock in T. cruzi.