Identification of novel snRNA-specific Sm proteins that bind selectively to U2 and U4 snRNAs in Trypanosoma brucei
Abstract
In eukaryotes the seven Sm core proteins bind to U1, U2, U4, and U5 snRNAs. In Trypanosoma brucei, Sm proteins have been implicated in binding both spliced leader (SL) and U snRNAs. In this study, we examined the function of these Sm proteins using RNAi silencing and protein purification. RNAi silencing of each of the seven Sm genes resulted in accumulation of SL RNA as well as reduction of several U snRNAs. Interestingly, U2 was unaffected by the loss of SmB, and both U2 and U4 snRNAs were unaffected by the loss of SmD3, suggesting that these snRNAs are not bound by the heptameric Sm complex that binds to U1, U5, and SL RNA. RNAi silencing and protein purification showed that U2 and U4 snRNAs were bound by a unique set of Sm proteins that we termed SSm (specific spliceosomal Sm proteins). This is the first study that identifies specific core Sm proteins that bind only to a subset of spliceosomal snRNAs.
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Footnotes
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Reprint requests to: Shulamit Michaeli, The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Geha Street, Ramat-Gan 52900, Israel; e-mail: michaes{at}mail.biu.ac.il; fax: 972-3-5351824.
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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.174307.
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- Received June 1, 2006.
- Accepted September 28, 2006.
- Copyright © 2007 RNA Society
