A exonuclease XRNA e o metabolismo de mRNA em Trypanosoma cruzi

Regulation of gene expression in trypanosomatids occurs mostly by post-transcriptional events. Some events involve changes in stability or access of mRNAs to translation that are directly related to adaptation of parasites during the life cycle. RNA granules, as p-dies and stress granules, comprise mRNPs that are responsible for regulating gene expression at pos-trancriptional level. Stress granules are involved in sorting and storage of mRNAs, whereas the P-bodies are sites for degradation of several transcripts. In the case of trypanosomatids, some proteins specific of stress granules and P-bodies have been identified, as DHH1, LSM1-7, SCD6, POP2 and XRNA proteins. However, the role of these parasite granules are still not clear. For example, T.cruzi DHH1 is in cytoplasmic mRNA granules independent of polysomes that are similar to both stress granules and P-bodies of yeast and mammalian. For this reason, it was not possible to define if DHH1 granules are involved specifically in mRNAs storage or degradation. Therefore, we have decided to investigate the role of the exonuclease TcXRNA and your association with mRNA granules in T. cruzi to help in sorting the the role of these granules. We have found that TcXRNA, an exonuclease 5 '→ 3' conserved and considered a P-body marker in yeast and mammals, is constitutively expressed throughout T.cruzi metacyclogenesis. It is localized mainly as cytoplasmic foci that the number is altered when the cells are under stress conditions or drug treatment that blocks the translation. Besides, TcXRNA and TcDHH1 seems to co-localize partially in epimastigotes that is reduced during parasite differentiation. We have observed that TcXRNA is present in cytoplasmic granules around the nucleus. The localization is similar to the perinuclear granules of Drosophila oocytes, but it is still necessary to investigate the functional relation between them. At this point, we are putting efforts in imunoprecipitation assays followed by mass spectrometry and hightroughput sequencing of RNAs, using parasites that express the Tagged-protein. Then, we intend to identify other components of these granules and the target RNAs, searching for better understand the functions of those mRNPs. So far, the data indicate the TcXRNA granules are dynamic and might be involved in mRNA metabolism having an important role in controlling the gene expression in T.cruzi.