title: Polycistronic trypanosome mRNAs are a target for the exosome.
abstract: Eukaryotic cells have several mRNA quality control checkpoints to avoid the production of aberrant proteins. Intron-containing mRNAs are actively degraded by the nuclear exosome, prevented from nuclear exit and, if these systems fail, degraded by the cytoplasmic NMD machinery. Trypanosomes have only two introns. However, they process mRNAs from long polycistronic precursors by trans-splicing and polycistronic mRNA molecules frequently arise from any missed splice site. Here, we show that RNAi depletion of the trypanosome exosome, but not of the cytoplasmic 5'-3' exoribonuclease XRNA or the NMD helicase UPF1, causes accumulation of oligocistronic mRNAs. We have also revisited the localization of the trypanosome exosome by expressing eYFP-fusion proteins of the exosome subunits RRP44 and RRP6. Both proteins are significantly enriched in the nucleus. Together with published data, our data suggest a major nuclear function of the trypanosome exosome in rRNA, snoRNA and mRNA quality control.
authors.affiliation: Biozentrum, Julius-Maximilians Universität Würzburg, Am Hubland, 97074 Würzburg, Germany; Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK. Electronic address: susanne.kramer@uni-wuerzburg.de.
authors.forename: Susanne
authors.initials: S
authors.lastname: Kramer
authors.affiliation: Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK.
authors.forename: Sophie
authors.initials: S
authors.lastname: Piper
authors.affiliation: Instituto de Parasitología y Biomedicina "López-Neyra", IPBL N-CSIC, Parque Tecnológico de Ciencias de la Salud, Avda. del Conocimiento, s/n.18100 Armilla, Granada, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Estevez
authors.affiliation: Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK.
authors.forename: Mark
authors.initials: M
authors.lastname: Carrington
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism; D063326:Exosome Multienzyme Ribonuclease Complex / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D016053:RNA, Protozoan / Q000235:genetics / Q000378:metabolism*; D020040:Trans-Splicing; D014346:Trypanosoma brucei brucei / Q000166:cytology / Q000235:genetics* / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D016053:RNA, Protozoan; D063326:Exosome Multienzyme Ribonuclease Complex
keywords: Exosome; NMD; Polycistronic mRNA; Trypanosoma brucei; Trypanosomes; trans-splicing