Key result
TcSub2 is an essential nuclear protein in trypanosomes associated with active RNA polymerase II, and its knockdown leads to nuclear mRNA accumulation and decreased translation.
TcSub2 is an essential nuclear protein in trypanosomes that functions as a component of the mRNA transcription/export pathway.
May identify antiparasitic targets; leaves open selective inhibition in human disease.
In eukaryotic cells, different RNA species are exported from the nucleus via specialized pathways. The mRNA export machinery is highly integrated with mRNA processing, and includes a different set of nuclear transport adaptors as well as other mRNA binding proteins, RNA helicases, and NPC-associated proteins. The protozoan parasite Trypanosoma cruzi is the causative agent of Chagas disease, a widespread and neglected human disease which is endemic to Latin America. Gene expression in Trypanosoma has unique characteristics, such as constitutive polycistronic transcription of protein-encoding genes and mRNA processing by trans-splicing. In general, post-transcriptional events are the major points for regulation of gene expression in these parasites. However, the export pathway of mRNA from the nucleus is poorly understood. The present study investigated the function of TcSub2, which is a highly conserved protein ortholog to Sub2/ UAP56, a component of the Transcription/Export (TREX) multiprotein complex connecting transcription with mRNA export in yeast/human. Similar to its orthologs, TcSub2 is a nuclear protein, localized in dispersed foci all over the nuclei -except the fibrillar center of nucleolus- and at the interface between dense and non-dense chromatin areas, proposing the association of TcSub2 with transcription/processing sites. These findings were analyzed further by BrUTP incorporation assays and confirmed that TcSub2 is physically associated with active RNA polymerase II (RNA pol II), but not RNA polymerase I (RNA pol I) or Spliced Leader (SL) transcription, demonstrating participation particularly in nuclear mRNA metabolism in T. cruzi. The double knockout of the TcSub2 gene is lethal in T. cruzi, suggesting it has an essential function. Alternatively, RNA interference assays were performed in Trypanosoma brucei. It allowed demonstrating that besides being an essential protein, its knockdown causes mRNA accumulation in the nucleus and decrease of translation levels, reinforcing that Trypanosoma-Sub2 (Tryp-Sub2) is a component of mRNA transcription/export pathway in trypanosomes.
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Serpeloni et al. (2011) studied Trypanosoma cruzi and Trypanosoma brucei (Chagas disease models). TcSub2 gene knockout and TbSub2 RNA interference vs. Wild-type or non-induced parasites was evaluated on Cell viability, mRNA distribution, and translation levels. TcSub2 is an essential nuclear protein in trypanosomes associated with active RNA polymerase II, and its knockdown leads to nuclear mRNA accumulation and decreased translation.
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