Bloodstream form Trypanosoma brucei do not require mRPN1 for gRNA processing.

Mitochondrial RNA processing in the kinetoplastid parasite Trypanosoma brucei involves numerous specialized catalytic activities that are incompletely understood. The mitochondrial genome consists of maxicircles that primarily encode rRNAs and mRNAs, and minicircles that encode a diverse array of guide RNAs (gRNAs). RNA editing uses these gRNAs as templates to recode mRNAs by insertion and deletion of uridine (U) residues. While the multiprotein complex that catalyzes RNA editing has been extensively studied, other players involved in mitochondrial RNA processing have remained enigmatic. The proteins required for processing mitochondrial polycistronic transcripts into mature species was essentially unknown until an RNase III endonuclease, called mRPN1, was reported to be involved in gRNA processing in procyclic form parasites. In this work, we examine the role of mRPN1 in gRNA processing in bloodstream form parasites, and show that complete elimination of mRPN1 by gene knockout does not alter gRNA maturation. These results indicate that another enzyme must be involved in gRNA processing.