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EMBO J. 2008 Jun 4;27(11):1596-608. doi: 10.1038/emboj.2008.87. Epub 2008 May 8.

3' adenylation determines mRNA abundance and monitors completion of RNA editing in T. brucei mitochondria.

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Department of Microbiology and Molecular Genetics, School of Medicine, University of California, Irvine, CA 92697, USA.


Expression of the mitochondrial genome in protozoan parasite Trypanosoma brucei is controlled post-transcriptionally and requires extensive U-insertion/deletion mRNA editing. In mitochondrial extracts, 3' adenylation reportedly influences degradation kinetics of synthetic edited and pre-edited mRNAs. We have identified and characterized a mitochondrial poly(A) polymerase, termed KPAP1, and determined major polypeptides in the polyadenylation complex. Inhibition of KPAP1 expression abrogates short and long A-tails typically found in mitochondrial mRNAs, and decreases the abundance of never-edited and edited transcripts. Pre-edited mRNAs are not destabilized by the lack of 3' adenylation, whereas short A-tails are required and sufficient to maintain the steady-state levels of partially edited, fully edited, and never-edited mRNAs. The editing directed by a single guide RNA is sufficient to impose a requirement for the short A-tail in edited molecules. Upon completion of the editing process, the short A-tails are extended as (A/U) heteropolymers into structures previously thought to be long poly(A) tails. These data provide the first direct evidence of functional interactions between 3' processing and editing of mitochondrial mRNAs in trypanosomes.

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