Characterization of a TFIIH homologue from<i>Trypanosoma brucei</i>

Lecordier, Laurence; Devaux, Sara; Uzureau, Pierrick; Dierick, Jean‐François; Walgraffe, David; Poelvoorde, Philippe; Pays, Étienne; Vanhamme, Luc

doi:10.1111/j.1365-2958.2007.05725.x

Cited by 31 publications

(44 citation statements)

References 80 publications

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“…Another observation was that the TFIIH signal appeared to be present in the nucleolar area, which by DAPI staining is apparent as a spherical structure with reduced staining, whereas the Med-T signal always was excluded from this area. This finding supports a previous study in which the silencing of the TFIIH subunit gene XPD affected nucleolusbased RNA pol I-mediated transcription (26). Med-T is essential for parasite viability and important for SLRNA transcription in vivo.…”

Section: Resultssupporting

confidence: 81%

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A TFIIH-Associated Mediator Head Is a Basal Factor of Small Nuclear Spliced Leader RNA Gene Transcription in Early-Diverged Trypanosomes

Lee

Wang

Panigrahi

et al. 2010

Molecular and Cellular Biology

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Genome annotation suggested that early-diverged kinetoplastids possess a reduced set of basal transcription factors. More recent work, however, on the lethal parasite Trypanosoma brucei identified extremely divergent orthologs of TBP, TFIIA, TFIIB, and TFIIH which, together with the small nuclear RNA-activating protein complex, form a transcription preinitiation complex (PIC) at the spliced leader (SL) RNA gene (SLRNA) promoter. The SL RNA is a small nuclear RNA and a trans splicing substrate for the maturation of all pre-mRNAs which is metabolized continuously to sustain gene expression. Here, we identified and biochemically characterized a novel TFIIH-associated protein complex in T. brucei (Med-T) consisting of nine subunits whose amino acid sequences are conserved only among kinetoplastid organisms. Functional analyses in vivo and in vitro demonstrated that the complex is essential for cell viability, SLRNA transcription, and PIC integrity. Molecular structure analysis of purified Med-T and Med-T/TFIIH complexes by electron microscopy revealed that Med-T corresponds to the mediator head module of higher eukaryotes. These data therefore show that mediator is a basal factor for small nuclear SL RNA gene transcription in trypanosomes and that the basal transcription function of mediator head is a characteristic feature of eukaryotes which developed early in their evolution.

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Section: Resultssupporting

confidence: 81%

“…The identification of TFIIA-2 and TFIIB suggested that trypanosomes harbor a full set of GTFs. Accordingly, TFIIH was found to be indispensable for SLRNA transcription (26,28).…”

mentioning

confidence: 99%

A TFIIH-Associated Mediator Head Is a Basal Factor of Small Nuclear Spliced Leader RNA Gene Transcription in Early-Diverged Trypanosomes

Lee

Wang

Panigrahi

et al. 2010

Molecular and Cellular Biology

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“…Similar cytological phenotypes result from blocking various processes. These include knockdowns of a mitotic cyclin or subunits of the transcription factor IIH (TFIIH) homolog in PF T. brucei (Hammarton et al 2003;Tu et al 2006;Lecordier et al 2007). Repression of a PHO80 homolog (CycE1/CYC2) results in cell cycle arrest at the G 1 /S checkpoint and generates slender zoids of T. brucei, while repression of a B-type cyclin homolog (CycB2) results in cell cycle arrest at the G 2 /M transition and generates stumpy zoids (Li and Wang 2003).…”

Section: Cell Viabilitymentioning

confidence: 99%

The MRB1 complex functions in kinetoplastid RNA processing

Acestor¹,

Panigrahi²,

Carnes³

et al. 2008

RNA

100

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Mitochondrial (mt) gene expression in Trypanosoma brucei entails multiple types of RNA processing, including polycistronic transcript cleavage, mRNA editing, gRNA oligouridylation, and mRNA polyadenylation, which are catalyzed by various multiprotein complexes. We examined the novel mitochondrial RNA-binding 1 (MRB1) complex that has 16 associated proteins, four of which have motifs suggesting RNA interaction. RNase treatment or the lack of kDNA in mutants resulted in lower MRB1 complex sedimentation in gradients, indicating that MRB1 complex associates with kDNA transcripts. RNAi knockdowns of expression of the Tb10.406.0050 (TbRGGm, RGG motif), Tb927.6.1680 (C2H2 zinc finger), and Tb11.02.5390 (no known motif) MRB1 proteins each inhibited in vitro growth of procyclic form parasites and resulted in cells with abnormal numbers of nuclei. Knockdown of TbRGGm, but not the other two proteins, disrupted the MRB1 complex, indicating that it, but perhaps not the other two, is required for complex assembly and/or stability. The knockdowns resulted in similar but nonidentical patterns of altered in vivo abundances of edited, pre-edited, and preprocessed mt mRNAs, but did not appreciably affect the abundances of mRNAs that do not get edited. These results indicate that MRB1 complex is critical to the processing of mt RNAs, and although its specific function is unknown, it appears essential to parasite viability.

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“…The second subcomplex, called the cyclin-activating kinase complex, contains CDK7-cyclin H and the Mat1 protein. The trypanosome TFIIH core complex has been partially characterized by two groups (32,33). The XPD subunit was identified by bioinformatics, and then tightly associated proteins were analyzed using TAP-tagged, XPD-containing T. brucei cell lines.…”

Section: General Transcription Factors In Trypanosome Rna Pol Ii-depementioning

confidence: 99%

RNA Polymerase Transcription Machinery in Trypanosomes

2008

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Transcription is a fundamental biological process employed by all living organisms to decode their genetic information. The information stored in genomic DNA is copied into RNA molecules by polymerization of ribonucleotide building blocks, which ultimately gives rise to different classes of transcripts. mRNAs encode polypeptides, rRNAs drive the macromolecular protein-synthesis machinery, and tRNAs act as adaptor molecules to assemble amino acids into proteins. Synthesis of specific transcripts is influenced by environmental and internal cell signals, which in turn are pivotal for the control of cellular regulatory networks.Trypanosomes are unicellular parasitic protozoa, members of the order Kinetoplastidae, which diverged early during evolution. They cause a wide range of debilitating diseases in humans and domestic animals. Trypanosoma brucei, known as the African trypanosome, is transmitted by tsetse flies in subSaharan Africa (15). Infection fulminates into African sleeping sickness in humans and nagana in animals (3). T. brucei is a digenetic parasite that cycles as a procyclic form in the digestive tract of the tsetse vector and as an extracellular bloodstream form in its mammalian host. During its complex life cycle, the parasite passes through five successive morphologically distinct forms (39). Parasites change from the procyclic form, which is characterized by a procyclic-specific surface coat, through two morphologically distinct forms in the fly and then they emerge as long, slender bloodstream forms, covered with a variant surface glycoprotein coat. Once inside the mammalian host, the long slender bloodstream form actively divides and establishes parasitemia. In the late phases of infection, the morphology of the parasite changes to nondividing short stumpy forms, which are ready to be taken up by the insect during a blood meal. The bloodstream form, with a rudimentary mitochondrion, is perfectly adapted to utilize the abundant supply of glucose from the mammalian blood and generate sufficient energy by glycolysis. The insect form, on the other hand, has a functional mitochondrion and generates most of its energy by respiration. These necessary metabolic adaptations depend upon a precise orchestration of numerous metabolic and cell biological activities.Studies of trypanosomes have uncovered several unusual biological phenomena (6). Notable among them are trans splicing and RNA editing (reviewed in references 7, 35, 46, 48, and 59). Protein-coding genes in trypanosomes are transcribed as long polycistronic precursor RNAs. Individual mature mRNAs are formed by trans splicing of a 39-nucleotide spliced leader (SL) RNA at the 5Ј end and subsequent 3Ј end maturation. RNA editing, used to produce mitochondrial mRNA, requires extensive alterations of primary transcripts by guide RNAs. Although guide RNA-dependent RNA editing is uniquely observed in trypanosomes, trans splicing has subsequently been observed in several other lower eukaryotes, including nematodes, trematodes, euglenoids, and chordates. The...

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Characterization of a TFIIH homologue fromTrypanosoma brucei

Cited by 31 publications

References 80 publications

A TFIIH-Associated Mediator Head Is a Basal Factor of Small Nuclear Spliced Leader RNA Gene Transcription in Early-Diverged Trypanosomes

A TFIIH-Associated Mediator Head Is a Basal Factor of Small Nuclear Spliced Leader RNA Gene Transcription in Early-Diverged Trypanosomes

The MRB1 complex functions in kinetoplastid RNA processing

RNA Polymerase Transcription Machinery in Trypanosomes

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