Compositionally and functionally distinct editosomes in Trypanosoma brucei
Abstract
Uridylate insertion/deletion RNA editing in Trypanosoma brucei mitochondria is catalyzed by a multiprotein complex, the ∼20S editosome. Editosomes purified via three related tagged RNase III proteins, KREN1 (KREPB1/TbMP90), KREPB2 (TbMP67), and KREN2 (KREPB3/TbMP61), had very similar but nonidentical protein compositions, and only the tagged member of these three RNase III proteins was identified in each respective complex. Three new editosome proteins were also identified in these complexes. Each tagged complex catalyzed both precleaved insertion and deletion editing in vitro. However, KREN1 complexes cleaved deletion but not insertion editing sites in vitro, and, conversely, KREN2 complexes cleaved insertion but not deletion editing sites. These specific nuclease activities were abolished by mutations in the putative RNase III catalytic domain of the respective proteins. Thus editosomes appear to be heterogeneous in composition with KREN1 complexes catalyzing cleavage of deletion sites and KREN2 complexes cleaving insertion sites while both can catalyze the U addition, U removal, and ligation steps of editing.
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Footnotes
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↵3 Present addresses: Program for Appropriate Technology in Health (PATH), Seattle, WA 98107, USA
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↵4 McGill University, Institute of Parasitology, Quebec H9X 3V9, Canada.
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Reprint requests to: Kenneth D. Stuart, Seattle Biomedical Research Institute, 307 Westlake Avenue N, Suite 500, Seattle, WA 98109, USA; e-mail: ken.stuart{at}sbri.org; fax: (206) 256-7229.
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Article published online ahead of print. Article and publication date are at http://www.rnajournal.org/cgi/doi/10.1261/rna.45506.
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- Received January 30, 2006.
- Accepted February 21, 2006.
- Copyright © 2006 RNA Society