TblncRNA-23, a long non-coding RNA transcribed by RNA polymerase I, regulates developmental changes in Trypanosoma brucei

genes are transcribed as polycistronic transcripts that are dissected into monocistronic transcripts by trans-splicing and polyadenylation. The two major surface proteins of procyclic (insect midgut) forms, EP and GPEET procyclin, are transcribed from a polycistronic transcription unit by polymerase I. Here we identified a long non-coding RNA termed TblncRNA-23 that is encoded between the two procyclin genes. TblncRNA-23 is 600 nt long and is partially localized to the nucleolus and partially associated with polysomes. Chimeric RNA molecules were identified between TblncRNA-23 and its targets. Overexpression of TblncRNA-23 identified its targets as EP and GPEET and other mRNAs that change in transition from early to late procyclic forms. These two forms differ in their social motility (SoMo)/pH sensing capabilities that are essential for migration from the insect midgut to enable parasite transmission. The interaction of TblncRNA-23 with its substrates is via base-pairing using different domains. Purification of TblncRNA-23 associated proteins in vivo by RaPID identified hundreds of proteins; among these are peptides synthesized from its target mRNAs, suggesting its association with translating ribosomes. Nucleolar TblncRNA-23 associates with multiple pre-rRNA processing factors, and cytoplasmic TblncRNA-23 with RNA binding proteins that regulate mRNA stability and translation. The overexpression of TblncRNA-23 resulted in parasites exhibiting hyper SoMo, suggesting its regulatory role in controlling SoMo and the parasite's potential to cycle between its hosts.