Abstract
We have recently shown in T. cruzi that a group of RNA Binding Proteins (RBPs), involved in mRNA metabolism, are accumulated into the nucleolus in response to Actinomycin D (ActD) treatment. In this work, we have extended our analysis to other members of the trypanosomatid lineage. In agreement with our previous study, the mechanism seems to be conserved in L. mexicana, since both endogenous RBPs and a transgenic RBP were relocalized to the nucleolus in parasites exposed to ActD. In contrast, in T. brucei, neither endogenous RBPs (TbRRM1 and TbPABP2) nor a transgenic RBP from T. cruzi were accumulated into the nucleolus under such treatment. Interestingly, when a transgenic TbRRM1was expressed in T. cruzi and the parasites exposed to ActD, TbRRM1 relocated to the nucleolus, suggesting that it contains the necessary sequence elements to be targeted to the nucleolus. Together, both experiments demonstrate that the mechanism behind nucleolar localization of RBPs, which is present in T. cruzi and L. mexicana, is not functional in T. brucei, suggesting that it has been lost or retained differentially during the evolution of the trypanosomatid lineage.
Highlights
Trypanosomes are protozoan parasites with sanitary relevance, since many members of this group of parasites are causative agents of important and neglected human diseases, such as Chagas disease in America and Sleeping sickness disease in Africa [1]
To know whether the mechanism responsible for the nucleolar relocalization of RNA Binding Proteins (RBPs) induced by Actinomycin D (ActD) in T. cruzi was conserved in other trypanosomatids, we evaluated the behaviour of the RBP LmxPABP2 (LmxM.34.4130) in L. mexicana promastigotes
When parasites were subjected to ActD, a transcriptional inhibitor which has extensively been used in several organisms, including trypanosomatids [25,26], for 24 h, LmxPABP2 was accumulated into the nucleolus in 63% of parasites, since it colocalized with the weakest area of staining with the DNA-specific dye DAPI and with the nucleolar antigen L1C6
Summary
Trypanosomes are protozoan parasites with sanitary relevance, since many members of this group of parasites are causative agents of important and neglected human diseases, such as Chagas disease in America and Sleeping sickness disease in Africa [1]. Trypanosomes are characterized by having complex life cycles alternating between vertebrate and invertebrate hosts, where they are exposed to different stress conditions that change abruptly [5,6]; several and rapid modifications at the gene expression level must be accomplished in order to readapt to such different conditions and niches [7] In this regard, the rapid formation of stress granules in response to starvation and severe heat shock [8,9], as well as the relocalization of certain of RNA Binding Proteins (RBPs) and poly(A)+ RNA to the nucleolus induced by particular stress conditions [10], might add another layer of rapid post-transcriptional regulation in these organisms
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