Identification and function of components from a divergent mRNA export pathway in trypanosomes

mRNA export is central to gene regulation and expression. In trypanosomes, transcription is polycistronic, all mRNAs are processed by trans-splicing and export is mediated by non-canonical mechanisms. We have described several conserved mRNA export pathway components in Trypanosoma cruzi, including orthologs of Sub2, a component of the TREX complex, and eIF4AIII, a core component of the exon junction complex (EJC). Few orthologs of proteins involved in mRNA export in higher eukaryotes are detectable in trypanosome genomes and examples of mechanistic divergence well known. To uncover additional components of the trypanosome mRNA maturation and export system we undertook an unbiased search for protein interactors of TcSub2 and TceIF4AIII. Significant overlap between TcSub2 and TceIF4AIII interacting protein cohorts suggests that both proteins associate with similar machinery. We confirmed several interactions with conserved core components of the EJC and multiple additional complexes, together with identification of proteins specific to trypanosomatids. The highly interactive super-interactome uncovered here, capable of supporting RNA processing from splicing through to nuclear export and cytoplasmic events, highlights kinetoplastid-specific and conserved components creating an amalgam to support the unique mRNA maturation mechanisms in trypanosomes.