Trans-splicing in the cestode Hymenolepis microstoma is constitutive across the life cycle and depends on gene structure and composition. Issue 2 (February 2023)

• Record Type: Journal Article
• Authors: Calvelo, Javier; Brehm, Klaus; Iriarte, Andrés; Koziol, Uriel
• Is Part Of: International journal for parasitology. Volume 53:Issue 2(2023)
• Page Start: 103
• Page End: 117
• Publication Date: 2023-02
• Subjects: Spliced leader -- Post-transcriptional regulation -- Tapeworm -- Flatworm -- Platyhelminthes; GO gene ontology -- mTP mitochondrial transit peptide -- pSL putative SL-RNA -- RT-PCR reverse transcription-PCR -- SJ splice junction -- SL spliced leader -- SM-site site for interacting with the spliceosome Sm proteins -- SP signal peptide -- TPM transcripts per million -- UTR untranslated region -- WRS test Wilcoxon Rank Signed test; Parasitology -- Periodicals; Parasitology -- Periodicals; Parasitologie -- Périodiques; Parasitology; Periodicals; Electronic journals; 571.999
• DOI: 10.1016/j.ijpara.2022.11.006
• Languages: English
• ISSNs: 0020-7519

Abstract

Graphical abstract: Highlights: Four spliced leader (SL)-RNAs are indiscriminately trans -spliced throughout the life cycle of Hymenolepis microstoma. Trans -splicing of polycistronic transcripts represents a minor proportion of events. Trans -splicing of monocistrons is associated with the acceptor sites of introns in the 5′ untranslated regions. Internal trans -splicing can result in isoforms with different predicted localizations. SL insertions can be used to improve existing gene models. Abstract: Spliced leader (SL) trans -splicing is a key process during mRNA maturation of many eukaryotes, in which a short sequence (SL) is transferred from a precursor SL-RNA into the 5′ region of an immature mRNA. This mechanism is present in flatworms, in which it is known to participate in the resolution of polycistronic transcripts. However, most trans -spliced transcripts are not part of operons, and it is not clear if this process may participate in additional regulatory mechanisms in this group. In this work, we present a comprehensive analysis of SL trans- splicing in the model cestode Hymenolepis microstoma . We identified four different SL-RNAs which are indiscriminately trans -spliced to 622 gene models. SL trans -splicing is enriched in constitutively expressed genes and does not appear to be regulated throughout the life cycle. Operons represented at least 20% of all detected trans -spliced gene models, showed conservation to those of the cestode Echinococcus multilocularis, and included complex loci such as an alternative operon (processed as either a single gene through cis -splicing or as two genes of a polycistron). Most insertion sites were identified in the 5′ untranslated region (UTR) of monocistronic genes. These genes frequently contained introns in the 5′ UTR, in which trans -splicing used the same acceptor sites as cis -splicing. These results suggest that, unlike other eukaryotes, trans -splicing is associated with internal intronic promoters in the 5′ UTR, resulting in transcripts with strong splicing acceptor sites without competing cis-donor sites, pointing towards a simple mechanism driving the evolution of novel SL insertion sites.