EpiRNomics in trypanosomatids impact on cycling of the parasites between the hosts

Trypanosomatids are the causative agent of African sleeping sickness, Leishmaniasis, and Chagas’ disease affecting millions of people worldwide. The parasites cycle between an insect and a mammalian host. The regulation of gene expression is post-transcriptionally and all mRNAs are processed by trans-splicing. rRNA processing involving additional steps generating fragmented rRNA. Here we will present our studies on the unique machinery that process the rRNA involving tens of protein factors and 15 unique trypanosome-specific small nucleolar RNAs (Chikne et al., NAR 2019). Genome-wide mapping of two most prevalent modifications on rRNAs and snRNA, pseudouridine (Y) and 2’-O-methylation (Nm) were performed on the two life stages and we found that rRNA is hypermodified in bloodstream form (BSF) trypanosomes (Chikne et al., Sci. Rep. 2016). Mutation introduced by CRISPR-Cas9 to the pseudouridine synthase CBF5 of small nucleolar (sno)RNAs that guide these modifications abolished transformation of procyclic to bloodstream form (BSF), suggesting that proper pseudouridylation is a pre-requisite for developmental cycling of the parasite. We will present the first whole genome-wide mapping of Ψ on small RNAs by and its implication on trans-splicing (Rajan et al., NAR 2019). Additionally, we will present high throughput mapping of 2’-O-methylation on rRNA that revealed 99 Nms similar to the number found in humans. Unlike in humans or yeast, depletion of individual critical modifications on rRNA affected ribosome biogenesis and growth of the parasite. The stage-specific modification revealed on the rRNA raise the intriguing possibility that the ribosome directly contribute to stage-specific translation regulation in these parasites.