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Updated: Aug 2, 2025

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The RNA export factor TbMex67 connects transcription and RNA export in Trypanosoma brucei and sets boundaries for RNA

Berta Pozzi1, Arunasalam Naguleswaran1, Francesca Florini1

  • 1Institute of Cell Biology, University of Bern, Bern, Switzerland.

Nucleic Acids Research
|April 18, 2023
PubMed

Insights

TbMex67 is crucial for mRNA export in trypanosomes. It connects transcription and export, preventing Pol I readthrough transcription and limiting R-loop formation.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Genetics

Background:

  • TbMex67 is a key mRNA export factor in trypanosomes, functioning at the nuclear pore.
  • Co-transcriptional mRNA export is a recently described process in Trypanosoma brucei.

Purpose of the Study:

  • To investigate the role of TbMex67 in co-transcriptional mRNA export in Trypanosoma brucei.
  • To understand how TbMex67 influences transcription by RNA Polymerase I (Pol I) and RNA Polymerase II (Pol II).

Main Methods:

  • Pulse labeling of nascent RNAs using 5-ethynyl uridine (5-EU).
  • Depletion of TbMex67 and complementation with a dominant-negative mutant (TbMex67-DN).
  • Analysis of RNA polymerase activity, R-loop formation, and histone modifications.

Main Results:

  • TbMex67 depletion and TbMex67-DN expression led to increased Pol I readthrough transcription at procyclin loci.
  • Pol I readthrough transcription resulted in read-through of genes and increased 5-EU incorporation.
  • TbMex67-DN increased Pol I-dependent R-loop formation and γ-histone 2A foci, with reduced nuclear localization and chromatin binding.

Conclusions:

  • TbMex67 connects transcription and mRNA export in T. brucei.
  • TbMex67 stalls Pol I readthrough transcription, thereby limiting R-loop formation and replication stress.

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