RNA Editing in Trypanosoma brucei Requires Three Different Editosomes

Abstract

Trypanosoma brucei has three distinct ∼20S editosomes that catalyze RNA editing by the insertion and deletion of uridylates. Editosomes with the KREN1 or KREN2 RNase III type endonucleases specifically cleave deletion and insertion editing site substrates, respectively. We report here that editosomes with KREPB2, which also has an RNase III motif, specifically cleave cytochrome oxidase II (COII) pre-mRNA insertion editing site substrates in vitro. Conditional repression and mutation studies also show that KREPB2 is an editing endonuclease specifically required for COII mRNA editing in vivo. Furthermore, KREPB2 expression is essential for the growth and survival of bloodstream forms. Thus, editing in T. brucei requires at least three compositionally and functionally distinct ∼20S editosomes, two of which distinguish between different insertion editing sites. This unexpected finding reveals an additional level of complexity in the RNA editing process and suggests a mechanism for how the selection of sites for editing in vivo is controlled.

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://mcb.asm.org/ .

ACKNOWLEDGMENTS

We thank Dan Golden and Stephen Hajduk for sharing unpublished results and members of the Stuart lab for discussions.

This study was supported by NIH grant GM042188 and initial joint support by AI014102. A.P. was supported by a Journal of Cell Science Traveling Fellowship. Research conducted using equipment made possible by Economic Development Administration-U.S. Department of Commerce and the M. J. Murdock Charitable Trust.