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A novel member of the RNase D exoribonuclease family functions in mitochondrial guide RNA metabolism in Trypanosoma brucei.

ABSTRACT: RNA turnover and RNA editing are essential for regulation of mitochondrial gene expression in Trypanosoma brucei. RNA turnover is controlled in part by RNA 3' adenylation and uridylation status, with trans-acting factors also impacting RNA homeostasis. However, little is known about the mitochondrial degradation machinery or its regulation in T. brucei. We have identified a mitochondrial exoribonuclease, TbRND, whose expression is highly up-regulated in the insect proliferative stage of the parasite. TbRND shares sequence similarity with RNase D family enzymes but differs from all reported members of this family in possessing a CCHC zinc finger domain. In vitro, TbRND exhibits 3' to 5' exoribonuclease activity, with specificity toward uridine homopolymers, including the 3' oligo(U) tails of guide RNAs (gRNAs) that provide the sequence information for RNA editing. Several lines of evidence generated from RNAi-mediated knockdown and overexpression cell lines indicate that TbRND functions in gRNA metabolism in vivo. First, TbRND depletion results in gRNA tails extended by 2-3 nucleotides on average. Second, overexpression of wild type but not catalytically inactive TbRND results in a substantial decrease in the total gRNA population and a consequent inhibition of RNA editing. The observed effects on the gRNA population are specific as rRNAs, which are also 3'-uridylated, are unaffected by TbRND depletion or overexpression. Finally, we show that gRNA binding proteins co-purify with TbRND. In summary, TbRND is a novel 3' to 5' exoribonuclease that appears to have evolved a function highly specific to the mitochondrion of trypanosomes.

SUBMITTER: Zimmer SL

PROVIDER: S-EPMC3060487 | biostudies-literature | 2011 Mar

REPOSITORIES: biostudies-literature

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A novel member of the RNase D exoribonuclease family functions in mitochondrial guide RNA metabolism in Trypanosoma brucei.

Zimmer Sara L SL McEvoy Sarah M SM Li Jun J Qu Jun J Read Laurie K LK

The Journal of biological chemistry 20110120 12

RNA turnover and RNA editing are essential for regulation of mitochondrial gene expression in Trypanosoma brucei. RNA turnover is controlled in part by RNA 3' adenylation and uridylation status, with trans-acting factors also impacting RNA homeostasis. However, little is known about the mitochondrial degradation machinery or its regulation in T. brucei. We have identified a mitochondrial exoribonuclease, TbRND, whose expression is highly up-regulated in the insect proliferative stage of the para ...[more]

PMID: 21252235

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Project description:The sleeping sickness parasite Trypanosoma brucei has a complex life cycle, alternating between a mammalian host and the tsetse fly vector. A tightly controlled developmental programme ensures parasite transmission between hosts as well as survival within them and involves strict regulation of mitochondrial activities. In the glucose-rich bloodstream, the replicative 'slender' stage is thought to produce ATP exclusively via glycolysis and uses the mitochondrial F1FO-ATP synthase as an ATP hydrolysis-driven proton pump to generate the mitochondrial membrane potential (??m). The 'procyclic' stage in the glucose-poor tsetse midgut depends on mitochondrial catabolism of amino acids for energy production, which involves oxidative phosphorylation with ATP production via the F1FO-ATP synthase. Both modes of the F1FO enzyme critically depend on FO subunit a, which is encoded in the parasite's mitochondrial DNA (kinetoplast or kDNA). Comparatively little is known about mitochondrial function and the role of kDNA in non-replicative 'stumpy' bloodstream forms, a developmental stage essential for disease transmission. Here we show that the L262P mutation in the nuclear-encoded F1 subunit ? that permits survival of 'slender' bloodstream forms lacking kDNA ('akinetoplastic' forms), via FO-independent generation of ??m, also permits their differentiation into stumpy forms. However, these akinetoplastic stumpy cells lack a ??m and have a reduced lifespan in vitro and in mice, which significantly alters the within-host dynamics of the parasite. We further show that generation of ??m in stumpy parasites and their ability to use ?-ketoglutarate to sustain viability depend on F1-ATPase activity. Surprisingly, however, loss of ??m does not reduce stumpy life span. We conclude that the L262P ? subunit mutation does not enable FO-independent generation of ??m in stumpy cells, most likely as a consequence of mitochondrial ATP production in these cells. In addition, kDNA-encoded genes other than FO subunit a are important for stumpy form viability.

Dataset Information

A novel member of the RNase D exoribonuclease family functions in mitochondrial guide RNA metabolism in Trypanosoma brucei.

Publications

A novel member of the RNase D exoribonuclease family functions in mitochondrial guide RNA metabolism in Trypanosoma brucei.

Similar Datasets

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