Posttranscriptional regulation of cytochrome c expression during the developmental cycle of Trypanosoma brucei.

Torri, Al F.; Hajduk, Stephen L.

doi:10.1128/mcb.8.11.4625

Cited by 50 publications

(20 citation statements)

References 48 publications

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“…4A). In addition, there is evidence that the developmental regulation of expression of cytochrome c and cytochrome c reductase is due to degradation of the proteins in the bloodstream form, perhaps because of failure of mitochondrial import (65,66,77,78). Experiments with trypanosomes with a soluble protein containing an N-terminal targeting signal for the mitochondrial matrix, and a C-terminal glycosomal targeting signal, have also shown that such signals can compete (28).…”

Section: Discussionmentioning

confidence: 99%

Characterization and Developmentally Regulated Localization of the Mitochondrial Carrier Protein Homologue MCP6 from Trypanosoma brucei

et al. 2006

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The order Kinetoplastida includes among its members a number of important human and veterinary pathogens, such as the African trypanosome Trypanosoma brucei (83). This parasite has a complex life cycle that alternates between the bloodstream form found in the blood and tissue fluids of mammals and the procyclic (insect) form in the midgut of the tsetse fly (46, 83). T. brucei undergoes a series of metabolic and morphological changes in order to adapt to these distinct host environments (45, 46). Bloodstream-form T. brucei metabolizes glucose to pyruvate and glycerol, obtaining ATP by substrate-level phosphorylation during glycolysis (48, 55). The mitochondria of this life form are highly reduced and lack key enzymes and components of the tricarboxylic acid cycle; their role in energy metabolism is probably restricted to the reoxidation of glycerol-3 phosphate by the mitochondrial alternative oxidase (20,48). This is in contrast to the procyclic form, which metabolizes amino acids and has a well-developed mitochondrion in which ATP is generated by a combination of substratelevel and oxidative phosphorylation (16,48,73,82).In both life forms of T. brucei, most of the glycolytic enzymes are found within a peroxisome-like organelle called the glycosome (14,48,60,61). This unique compartmentation of glycolytic enzymes has been shown to be essential for trypanosome survival (5,11,22,25,51). It has been proposed that the glycosomal membrane forms a barrier to ATP and ADP, insulating the enzymes of the glycosomal matrix from the ADP/ ATP ratio in the cytosol (5).So far, no glycosomal or mitochondrial metabolite carriers have been identified for T. brucei, although they most probably play a key role in the regulation of energy metabolism. The characterization of these carriers should make it possible to build more-accurate biochemical and mathematical models of trypanosome energy metabolism (5).The mitochondrial carrier family (MCF) was initially defined as a group of proteins that are located in the inner mitochondrial membrane and mediate the transport of a large range of metabolic intermediates (3,32,35,(57)(58)(59)86). Recently, several structurally and functionally related carrier proteins were also found in the membranes of peroxisomes (52,81,88,90). We therefore wondered whether such proteins might also be found in kinetoplastid glycosomes. The recently completed genome sequence of T. brucei (8) contains about 29 genes encoding different proteins of the mitochondrial carrier family. In this paper, we describe the characterization of MCP6, a novel mitochondrial carrier protein homologue from T. brucei. MATERIALS AND METHODSCulture and transfection. Trypanosoma brucei cell lines were cultured in either HMI-9 medium for bloodstream cell lines (29) or MEM-PROS medium for procyclic cell lines (56), supplemented with 10% (vol/vol) fetal calf serum (Sigma-Aldrich). Cells were transfected as described previously (9). In all experiments, "wild type" refers to bloodstream or procyclic T. brucei strain

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Section: Discussionmentioning

confidence: 99%

Characterization and Developmentally Regulated Localization of the Mitochondrial Carrier Protein Homologue MCP6 from Trypanosoma brucei

et al. 2006

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“…A similar analysis of mitochondrial encoded proteins led to the identification of an alternatively edited COIII mRNA that encoded a component of the FKC (32,40). The developmental regulation of nuclear-encoded mitochondrial proteins in T. brucei occurs principally at the level of RNA stability and, to a lesser extent, by differential protein stability (41,42). High-throughput RNA sequencing (RNA-Seq) provides an accurate evaluation of the life cycle-dependent expression of mitochondrial proteins (43)(44)(45)(46).…”

Section: Resultsmentioning

confidence: 99%

Dual Functions of α-Ketoglutarate Dehydrogenase E2 in the Krebs Cycle and Mitochondrial DNA Inheritance in Trypanosoma brucei

Sykes

Hajduk

2013

Eukaryot Cell

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The dihydrolipoyl succinyltransferase (E2) of the multisubunit ␣-ketoglutarate dehydrogenase complex (␣-KD) is an essential Krebs cycle enzyme commonly found in the matrices of mitochondria. African trypanosomes developmentally regulate mitochondrial carbohydrate metabolism and lack a functional Krebs cycle in the bloodstream of mammals. We found that despite the absence of a functional ␣-KD, bloodstream form (BF) trypanosomes express ␣-KDE2, which localized to the mitochondrial matrix and inner membrane. Furthermore, ␣-KDE2 fractionated with the mitochondrial genome, the kinetoplast DNA (kDNA), in a complex with the flagellum. A role for ␣-KDE2 in kDNA maintenance was revealed in ␣-KDE2 RNA interference (RNAi) knockdowns. Following RNAi induction, bloodstream trypanosomes showed pronounced growth reduction and often failed to equally distribute kDNA to daughter cells, resulting in accumulation of cells devoid of kDNA (dyskinetoplastic) or containing two kinetoplasts. Dyskinetoplastic trypanosomes lacked mitochondrial membrane potential and contained mitochondria of substantially reduced volume. These results indicate that ␣-KDE2 is bifunctional, both as a metabolic enzyme and as a mitochondrial inheritance factor necessary for the distribution of kDNA networks to daughter cells at cytokinesis.

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“…Procyclic (insect) form parasites contain a fully functional mitochondrion that carries out oxidative phosphorylation (3,29,42). In contrast, bloodstream (mammalian) form trypanosomes exhibit a high rate of glycolysis and contain an underdeveloped mitochondrion (3,29,42). Similar to other eukaryotes, the genes for the mitochondrial proteins are encoded both in the nuclear and mitochondrial genomes.…”

mentioning

confidence: 92%

“…It contains a single large mitochondrion, whose gene expression and metabolic activity are regulated throughout its life cycle. Procyclic (insect) form parasites contain a fully functional mitochondrion that carries out oxidative phosphorylation (3,29,42). In contrast, bloodstream (mammalian) form trypanosomes exhibit a high rate of glycolysis and contain an underdeveloped mitochondrion (3,29,42).…”

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confidence: 99%

Opposing Effects of Polyadenylation on the Stability of Edited and Unedited Mitochondrial RNAs in Trypanosoma brucei

Kao

Read

2005

Molecular and Cellular Biology

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Mitochondrial RNAs in Trypanosoma brucei undergo posttranscriptional RNA editing and polyadenylation. We previously showed that polyadenylation stimulates turnover of unedited RNAs. Here, we investigated the role of polyadenylation in decay of edited RPS12 RNA. In in vitro turnover assays, nonadenylated fully edited RNA degrades significantly faster than its unedited counterpart. Rapid turnover of nonadenylated RNA is facilitated by editing at just six editing sites. Surprisingly, in direct contrast to unedited RNA, turnover of fully edited RNA is dramatically slowed by addition of a poly(A) 20 tail. The same minimal edited sequence that stimulates decay of nonadenylated RNA is sufficient to switch the poly(A) tail from a destabilizing to a stabilizing element. Both nucleotide composition and length of the 3 extension are important for stabilization of edited RNA. Titration of poly(A) into RNA degradation reactions has no effect on turnover of polyadenylated edited RNA. These results suggest the presence of a protective protein(s) that simultaneously recognizes the poly(A) tail and small edited element and which blocks the action of a 3-5 exonuclease. This study provides the first evidence for opposing effects of polyadenylation on RNA stability within a single organelle and suggests a novel and unique regulation of RNA turnover in this system.Trypanosoma brucei is a unicellular, flagellated, parasitic protozoan that causes African sleeping sickness in humans and nagana in domestic livestock. It contains a single large mitochondrion, whose gene expression and metabolic activity are regulated throughout its life cycle. Procyclic (insect) form parasites contain a fully functional mitochondrion that carries out oxidative phosphorylation (3,29,42). In contrast, bloodstream (mammalian) form trypanosomes exhibit a high rate of glycolysis and contain an underdeveloped mitochondrion (3,29,42). Similar to other eukaryotes, the genes for the mitochondrial proteins are encoded both in the nuclear and mitochondrial genomes.Since transcription of T. brucei mitochondrial DNA generates polycistronic transcripts (14,19,22,33), posttranscriptional mechanisms of gene expression and their regulation are of prime importance. Maturation of mitochondrial RNAs requires several posttranscriptional processing steps, including precursor cleavage, RNA editing, and polyadenylation. Polycistronic precursors must be endonucleolytically cleaved and possibly exonucleolytically trimmed to create the correct 5Ј and 3Ј ends of individual monocistronic RNAs. In addition, 12 of the 18 transcripts in T. brucei mitochondria require editing, which involves specific insertion and deletion of uridine residues, to create translatable RNAs (for recent reviews see references 27, 37, 38, and 40). mRNAs are also extended at their 3Ј ends by polyadenylation. The length of poly(A) tail has been found to correlate with the edited status of the RNA. While unedited RNAs contain either no or short (ϳ20 nucleotides [nt]) poly(A) tails, edited RNAs, including partia...

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Posttranscriptional regulation of cytochrome c expression during the developmental cycle of Trypanosoma brucei.

Cited by 50 publications

References 48 publications

Characterization and Developmentally Regulated Localization of the Mitochondrial Carrier Protein Homologue MCP6 from Trypanosoma brucei

Characterization and Developmentally Regulated Localization of the Mitochondrial Carrier Protein Homologue MCP6 from Trypanosoma brucei

Dual Functions of α-Ketoglutarate Dehydrogenase E2 in the Krebs Cycle and Mitochondrial DNA Inheritance in Trypanosoma brucei

Opposing Effects of Polyadenylation on the Stability of Edited and Unedited Mitochondrial RNAs in Trypanosoma brucei

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