Key result
Treatment with leptomycin B eliminated cytoplasmic SL RNA in T. brucei, demonstrating that cytoplasmic SL RNA is dependent on the nuclear exporter exportin 1 (XPO1) for biogenesis.
The study demonstrates that exportin 1 mediates the nuclear export of kinetoplastid spliced leader RNA, revealing similarities with metazoan small nuclear RNA trafficking.
Extends parallels in snRNA trafficking across eukaryotes; leaves open XPO1 as a potential antiparasitic target.
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.
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Zeiner et al. (2003) studied this question. Leptomycin B was evaluated on SL RNA localization and biogenesis. Treatment with leptomycin B eliminated cytoplasmic SL RNA in T. brucei, demonstrating that cytoplasmic SL RNA is dependent on the nuclear exporter exportin 1 (XPO1) for biogenesis.
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