Abstract
RNA-binding proteins play a particularly important role in regulating gene expression in trypanosomes. A map of the network of protein complexes in Trypanosoma brucei uncovered an essential protein (Tb927.10.7910) that is postulated to be an RNA-binding protein implicated in the regulation of the mitochondrial post-transcriptional gene regulatory network by its association with proteins that participate in a multi-protein RNA editing complex. However, the mechanism by which this protein interacts with its multiple target transcripts remained unknown. Using sensitive database searches and experimental data, we identify Z-DNA-binding domains in T. brucei in the N- and C-terminal regions of Tb927.10.7910. RNA-binding studies of the wild-type protein, now referred to as RBP7910 (RNA binding protein 7910), and site-directed mutagenesis of residues important for the Z-DNA binding domains show that it preferentially interacts with RNA molecules containing poly(U) and poly(AU)-rich sequences. The interaction of RBP7910 with these regions may be involved in regulation of RNA editing of mitochondrial transcripts.
Highlights
One of the most intriguing features of Trypanosoma brucei, a unicellular kinetoplastid parasite, is its unique way of producing energy in different life cycle stages1
Editing relies on mitochondrial-encoded small RNAs known as guide RNAs which contain the information needed for the proper addition of uridines to or deletion from pre-mRNAs to produce edited-mRNAs, which are translated into essential protein subunits of the respiratory chain
We previously reported a mitochondrial protein (Tb927.10.7910) that interacts with REMC5A and TbRGG2, subunits in the RNA editing substrate-binding complex (RESC), in an RNA-dependent manner28
Summary
One of the most intriguing features of Trypanosoma brucei, a unicellular kinetoplastid parasite, is its unique way of producing energy in different life cycle stages. Editing relies on mitochondrial-encoded small RNAs known as guide RNAs (gRNA) which contain the information needed for the proper addition of uridines to or deletion from pre-mRNAs to produce edited-mRNAs, which are translated into essential protein subunits of the respiratory chain. Upon binding to the pre-mRNA, the gRNA 3′ (U)-tail interacts with the purine-rich region upstream of the editing site (ES). In addition to the editosome or RNA editing core complex (RECC), which catalyzes the enzymatic steps of the editing process, other dynamic multi-protein complexes have been identified. These include the RNA-editing mediator complex (REMC), guide RNA binding complex (GRBC), and the polyadenylation mediator complex (PAMC), collectively known as the RNA editing substrate-binding complex (RESC). This study illustrated the link between the PPsome and the RESC and its role in converting the mitochondrial transcription-defined 5′ terminus into a monophosphorylated state
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