Mapping and 5′ end determination of kinetoplast maxicircle gene transcripts from<i>Leishmania tarentolae</i>

Simpson, Agda M.; Neckelmann, Nicolas; Cruz, V F de la; Muhich, Michael L.; Simpson, Larry

doi:10.1093/nar/13.16.5977

Cited by 39 publications

(22 citation statements)

References 20 publications

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“…For example, the bifunctional dihydrofolate reductase-thymidylate synthase (DHFR-TS) gene is amplified when parasites are exposed over extended periods of time to the cytotoxic DHFR inhibitor methotrexate, and these mutants are highly resistant to methotrexate due to the pronounced increase in the level of the DHFR-TS target protein (42). This mechanism of resistance is unlikely to be available to parasites exposed to buparvaquone, because (i) amplification of the cytochrome b open reading frame does not achieve an increase in the level of the multisubunit protein and (ii) the cytochrome b gene is carried by mitochondrial maxicircle DNA (43) and not within the plastic nuclear genome.…”

Section: Discussionmentioning

confidence: 99%

Targeting the Cytochrome bc ₁ Complex of Leishmania Parasites for Discovery of Novel Drugs

Ortiz

Forquer

Boitz

et al. 2016

Antimicrob Agents Chemother

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c Endochin-like quinolones (ELQs) are potent and specific inhibitors of cytochrome bc 1 from Plasmodium falciparum and Toxoplasma gondii and show promise for novel antiparasitic drug development. To determine whether the mitochondrial electron transport chain of Leishmania parasites could be targeted similarly for drug development, we investigated the activity of 134 structurally diverse ELQs. A cohort of ELQs was selectively toxic to amastigotes of Leishmania mexicana and L. donovani, with 50% inhibitory concentrations (IC 50 s) in the low micromolar range, but the structurally similar hydroxynaphthoquinone buparvaquone was by far the most potent inhibitor of electron transport, ATP production, and intracellular amastigote growth. Cytochrome bc 1 is thus a promising target for novel antileishmanial drugs, and further improvements on the buparvaquone scaffold are warranted for development of enhanced therapeutics.

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Section: Discussionmentioning

confidence: 99%

Targeting the Cytochrome bc ₁ Complex of Leishmania Parasites for Discovery of Novel Drugs

Ortiz

Forquer

Boitz

et al. 2016

Antimicrob Agents Chemother

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“…The fact that the MURF2 genes of the related kinetoplastids Leishmania tarentolae and Crithidiafasciculata also lack genomic ATGs but have both additional uridines and created AUGs within the 5' ends of their transcripts (Shaw et al, submitted) supports this conclusion. The MURF2 gene has no detected homology to mitochondrial genes from other organisms except kinetoplastids (12,16,17), and the function of its putative protein product is unknown. Since uridines are added in both slender and procyclic forms, the protein product of MURF2 may function in both these life cycle stages.…”

Section: Discussionmentioning

confidence: 99%

“…They encode mitochondrial rRNAs and components of the mitochondrial respiratory system, including apocytochrome b (CYb); cytochrome oxidase subunits I and II (COI and COII); and NADH dehydrogenase subunits 1, 4, and 5 (ND1, ND4, and ND5). In addition, there are two open reading frames, MURF1 and MURF2, which probably encode proteins but have no detected homology to mitochondrial genes from other organisms (2,6,(12)(13)(14)17).…”

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Developmental aspects of uridine addition within mitochondrial transcripts of Trypanosoma brucei.

1988

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The mitochondrial respiratory system is absent in slender bloodstream forms of Trypanosoma brucei, incomplete in stumpy bloodstream forms, and complete in procyclic (insect) forms. The steady-state abundance of transcripts of some mitochondrially encoded components of the respiratory system correlates with its differential expression in different life cycle stages. Recently, it was reported that uridines which are not encoded in the genome are added to cytochrome b and cytochrome oxidase II transcripts. We now report that the (U)+ transcripts of both genes are found in procyclic forms and to some degree in stumpy forms but are absent in slender forms. The uridine additions to cytochrome oxidase II correct a frameshift in the gene and presumably allow production of a full-length protein, whereas those added to cytochrome b create an in-frame AUG which extends the N terminus of the predicted protein by 20 amino acids. The stage specificity of uridine additions to these transcripts thus reflects the life cycle stage during which the protein products would be used. Transcripts of MURF2, a gene of unknown function, have additional uridines in both slender and procyclic forms which create two in-frame AUGs. MURF2 transcripts additionally differ from the DNA sequence in ways which cannot be explained by uridine addition alone, implying that other processes alter these transcripts.

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“…The maxicircle protein coding regions are very compact, and many of the genes overlap extensively, leaving little room for regulatory sequences that might control transcription and RNA processing. It was shown previously that maxicircle transcription produces polycistronic RNAs that are processed to mature RNAs (16,27). The presence of such precursors indicates that the mature RNAs are generated by 3Ј-and 5Ј-end processing, which, for several of the overlapping genes, eliminates a portion of the coding regions of the adjacent transcripts, which then must be degraded.…”

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confidence: 97%

RBP38, a Novel RNA-Binding Protein from Trypanosomatid Mitochondria, Modulates RNA Stability

et al. 2003

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We describe here the isolation and characterization of a novel RNA-binding protein, RBP38, from Leishmania tarentolae mitochondria. This protein does not contain any known RNA-binding motifs and is highly conserved among the trypanosomatids, but no homologues were found in other organisms. Recombinant LtRBP38 binds single and double-stranded (ds) RNA substrates with dissociation constants in the 100 nM range, as determined by fluorescence polarization analysis. Downregulation of expression of the homologous gene, TbRBP38, in procyclic Trypanosoma brucei by using conditional dsRNA interference resulted in 80% reduction of steady-state levels of RNAs transcribed from both maxicircle and minicircle DNA. In organello pulse-chase labeling experiments were used to determine the stability of RNAs in mitochondria that were depleted of TbRBP38. The half-life of metabolically labeled RNA decreased from ϳ160 to ϳ60 min after depletion. In contrast, there was no change in transcriptional activity. These observations suggest a role of RBP38 in stabilizing mitochondrial RNA.RNA-binding proteins are involved in the synthesis, processing, transport, translation, degradation, and stabilization of RNA (7, 24). The mitochondrial genome of trypanosomatids is composed of thousands of circular DNA molecules, which are catenated and form a dense body of DNA, called the kinetoplast DNA network. This consists of two types of molecules: maxicircles and minicircles. The maxicircle encodes two rRNAs, 18 mRNAs, and a few gRNAs (2). The minicircle encodes the majority of the gRNAs (28). The maxicircle protein coding regions are very compact, and many of the genes overlap extensively, leaving little room for regulatory sequences that might control transcription and RNA processing. It was shown previously that maxicircle transcription produces polycistronic RNAs that are processed to mature RNAs (16,27). The presence of such precursors indicates that the mature RNAs are generated by 3Ј-and 5Ј-end processing, which, for several of the overlapping genes, eliminates a portion of the coding regions of the adjacent transcripts, which then must be degraded. Mitochondrial biogenesis in Trypanosoma brucei is developmentally regulated (23,26,29). In long slender bloodstream forms mitochondrial function is strongly repressed.During differentiation, the mitochondrion is partially activated in the short stumpy bloodstream form, but only in the insect midgut procyclic form is the mitochondrion fully active. This change in physiology is reflected in a stage-specific regulation of mitochondrial gene expression (15, 18). The levels of some mitochondrial transcripts in short stumpy cells are intermediate between the long slender and procyclic forms, whereas other transcripts are already at the procyclic levels. The transcription rates and processing of the rRNA genes are the same in the bloodstream and the procyclic forms, suggesting that the difference in abundance of the mature rRNAs is due to differential stability in the two forms of the life cycle (19). T...

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Mapping and 5′ end determination of kinetoplast maxicircle gene transcripts fromLeishmania tarentolae

Cited by 39 publications

References 20 publications

Targeting the Cytochrome bc ₁ Complex of Leishmania Parasites for Discovery of Novel Drugs

Targeting the Cytochrome bc ₁ Complex of Leishmania Parasites for Discovery of Novel Drugs

Developmental aspects of uridine addition within mitochondrial transcripts of Trypanosoma brucei.

RBP38, a Novel RNA-Binding Protein from Trypanosomatid Mitochondria, Modulates RNA Stability

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Mapping and 5′ end determination of kinetoplast maxicircle gene transcripts fromLeishmania tarentolae

Cited by 39 publications

References 20 publications

Targeting the Cytochrome bc 1 Complex of Leishmania Parasites for Discovery of Novel Drugs

Targeting the Cytochrome bc 1 Complex of Leishmania Parasites for Discovery of Novel Drugs

Developmental aspects of uridine addition within mitochondrial transcripts of Trypanosoma brucei.

RBP38, a Novel RNA-Binding Protein from Trypanosomatid Mitochondria, Modulates RNA Stability

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Targeting the Cytochrome bc ₁ Complex of Leishmania Parasites for Discovery of Novel Drugs

Targeting the Cytochrome bc ₁ Complex of Leishmania Parasites for Discovery of Novel Drugs