title: Exportin 1 mediates nuclear export of the kinetoplastid spliced leader RNA.
abstract: The kinetoplastid protozoan spliced leader (SL) RNA is the common substrate pre-mRNA utilized in all trans-splicing reactions. Here we show by fluorescence in situ hybridization that the SL RNA is present in the cytoplasm of Leishmania tarentolae and Trypanosoma brucei. Treatment with the karyopherin-specific inhibitor leptomycin B was toxic to T. brucei and eliminated the cytoplasmic SL RNA, suggesting that cytoplasmic SL RNA was dependent on the nuclear exporter exportin 1 (XPO1). Ectopic expression of xpo1 with a C506S mutation in T. brucei conferred resistance to leptomycin B. A reduction in SL RNA 3' extension removal and 5' methylation of nucleotide U(4) was observed in wild-type T. brucei treated with leptomycin B, suggesting that the cytoplasmic stage is necessary for SL RNA biogenesis. This study demonstrates spatial and mechanistic similarities between the posttranscriptional trafficking of the kinetoplastid protozoan SL RNA and the metazoan cis-spliceosomal small nuclear RNAs.
authors.affiliation: Department of Microbiology, University of California at Los Angeles, Los Angeles, California 90095-1489, USA.
authors.forename: Gusti M
authors.initials: GM
authors.lastname: Zeiner
authors.forename: Nancy R
authors.initials: NR
authors.lastname: Sturm
authors.forename: David A
authors.initials: DA
authors.lastname: Campbell
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000502:physiology; D000818:Animals; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism; D018105:DNA, Kinetoplast / Q000235:genetics / Q000378:metabolism*; D004351:Drug Resistance / Q000235:genetics; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D028884:Karyopherins / Q000235:genetics / Q000378:metabolism*; D007891:Leishmania / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D008745:Methylation / Q000187:drug effects; D009154:Mutation / Q000235:genetics; D012323:RNA Processing, Post-Transcriptional / Q000187:drug effects / Q000235:genetics; D020038:RNA, Spliced Leader / Q000235:genetics / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear; D020040:Trans-Splicing / Q000187:drug effects / Q000502:physiology; D014346:Trypanosoma brucei brucei / Q000235:genetics / Q000378:metabolism*; D000097606:Exportin 1 Protein
chemical_list: D018105:DNA, Kinetoplast; D005231:Fatty Acids, Unsaturated; D028884:Karyopherins; D020038:RNA, Spliced Leader; D018160:Receptors, Cytoplasmic and Nuclear; D000097606:Exportin 1 Protein; C038753:leptomycin B