Key result
Trypanosomes possess three distinct Mex67 paralogs, with TbMex67 and TbMex67b mediating mRNA export and TbMex67L primarily involved in ribosome biogenesis.
Why the study?
While most eukaryotes have one Mex67 gene, trypanosomes possess three distinct Mex67 paralogs and a single Mtr2 gene, leaving their functional roles in RNA export to be defined.
Trypanosomes possess three distinct Mex67 paralogs with differing and non-redundant roles in RNA export and ribosome biogenesis, indicating significant evolutionary divergence in RNA export mechanisms.
Answers are grounded in this paper and cite their sources.
Indicates divergent RNA export in parasites; leaves open whether paralog-specific inhibition could treat trypanosomiasis.
In opistokhonts (animals and fungi), mRNA export to the cytoplasm is mediated by the Mex67/Mtr2 (NXF1/NXT1) heterodimer via the nuclear pore complex (NPC). In contrast to most nucleocytoplasmic transport, mRNA export requires ATP-dependent remodeling machinery, and in animals and fungi is Ran-independent. While most eukaryotes possess one Mex67 gene, trypanosomes have three distinct Mex67 paralogs, while retaining a single Mtr2 gene. We show here that these paralogs, TbMex67, TbMex67b and TbMex67L, have differing and non-redundant roles in RNA export. Specifically, TbMex67 and TbMex67b retain a canonical role in mRNA export, albeit associating with specific mRNA cohorts, but in contrast, TbMex67L is primarily involved in ribosome biogenesis. Together with the association of all Mex67 paralogs with the Ran machinery, these findings indicate significant departures in RNA export mechanisms in these divergent organisms, with implications for evolutionary origins and diversity in control of gene expression.
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Obado et al. (2022) studied Trypanosoma brucei (parasite) biology. RNA interference (RNAi) of TbMex67 paralogs vs. Control cells was evaluated on Cell viability and RNA localization. Trypanosomes possess three distinct Mex67 paralogs, with TbMex67 and TbMex67b mediating mRNA export and TbMex67L primarily involved in ribosome biogenesis.
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