Split introns in the genome of Giardia intestinalis are excised by spliceosome-mediated trans-splicing |
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Authors: | Kamikawa Ryoma Inagaki Yuji Tokoro Masaharu Roger Andrew J Hashimoto Tetsuo |
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Institution: | 1 Center for Computational Sciences and Institute of Biological Sciences, University of Tsukuba, Ibaraki 305-8577, Japan 2 Department of Parasitology, Kanazawa University, Ishikawa 920-8640, Japan 3 Centre for Comparative Genomics and Evolutionary Bioinformatics, Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 1X5, Canada |
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Abstract: | Spliceosomal introns are hallmarks of most eukaryotic genomes and are excised from premature mRNAs by a spliceosome that is among the largest, and most complex, molecular machine in cells. The divergent unicellular eukaryote Giardia intestinalis, the causative agent of giardiasis, also possesses spliceosomes, but only four canonical (cis-spliced) introns have been identified in its genome to date. We demonstrate that this organism has a novel form of spliceosome-mediated trans-splicing of split introns that is essential for generating mature mRNAs for at least two important genes: one encoding a heat shock protein 90 (HSP90), which controls the conformation of a suite of cellular proteins, and the other encoding a dynein molecular motor protein, involved in the motility of eukaryotic flagella. These split introns have properties that distinguish them from other trans-splicing systems known within eukaryotes, suggesting that Giardia independently evolved a unique system to splice split introns. |
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