Alternative RNA Editing Produces a Novel Protein Involved in Mitochondrial DNA Maintenance in Trypanosomes

Abstract

The mitochondrial genome of trypanosomes is composed of thousands of topologically interlocked circular DNA molecules that form the kinetoplast DNA (kDNA). Most genes encoded by the kDNA require a posttranscriptional modification process called RNA editing to form functional mRNAs. Here, we show that alternative editing of the mitochondrial cytochrome c oxidase III (COXIII) mRNA in Trypanosoma brucei produces a novel DNA binding protein, alternatively edited protein 1 (AEP-1). AEP-1 localizes to the region of the cell between the kDNA and the flagellum and purifies with the tripartite attachment complex, a structure believed to physically link the kDNA and flagellar basal bodies. Expression of the DNA binding domain of AEP-1 results in aberrant kDNA structure and reduced cell growth, indicating that AEP-1 is involved in the maintenance of the kDNA. Perhaps most important, our studies show a gain of function through an alternatively edited mRNA and, for the first time, provide a link between the unusual structure of the kDNA and RNA editing in trypanosome mitochondria.

SUPPLEMENTAL MATERIAL

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

ACKNOWLEDGMENTS

We are grateful to Keith Gull for antibodies to the basal body, Minu Chaudhuri for antibodies to TAO, John Shields for excellent assistance with electron microscopy, Justin Widener and members of the Hajduk laboratory for discussion, and Justin Graham for initial expression of AEP1^(1-59)-His_10.

This work was supported by a grant from the National Institutes of Health (AI21401).