mRNAs Granules in Trypanosomes

CASSOLA, A; DE GAUDENZI, JG; FRASCH, AC

Woods Hole, USA

Congreso; Molecular Parasitology Meeting XVII; 2007

Metabolism of mRNA in Trypanosomes is of extreme importance in the regulation of gene expression, since these unicellular eukaryotes mostly control protein synthesis by post-transcriptional mechanisms. By using poly(A)+ mRNA Fluorescence In Situ Hybridization we show that mRNA in insect-stage trypanosomes has a heterogeneous cytoplasmic localization, occupying discrete portions of the cytoplasm. Under carbon source starvation, mRNA metabolism in these organisms involves recruitment of mRNAs and proteins to ribonucleoprotein granules in the cytoplasm. Transcripts in the translating pool can be targeted to these structures, where they are stored in a non-degradative manner. Recovery of parasites from starvation stress in rich medium disassembles mRNA granules, suggesting that transcripts could re-engage translation in polysomes. Trypanosomal mRNA granules are somehow similar to P bodies regarding protein content, but rather could have a similar function to Stress Granules in protecting transcripts than being degradation factories as P bodies. Although mRNA granules are formed after parasite starvation in axenic culture, they are also present naturally during the life cycle of Trypanosoma cruzi in the insect vector, but their formation is not a prerequisite for in vitro differentiation. We suggest that trypanosomes make use of mRNA granules for transient transcript protection as a strategy to cope with periods of starvation that they have to face during their complex life cycles.