The promoter and transcribed regions of the Leishmania tarentolae spliced leader RNA gene array are devoid of nucleosomes

Hitchcock, Robert A.; Thomas, Sean; Campbell, David A.; Sturm, Nancy R.

doi:10.1186/1471-2180-7-44

Cited by 23 publications

(23 citation statements)

References 59 publications

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“…3, pol II) (41,180). While in T. cruzi epimastigotes and L. tarentolae predominantly only one SL RNA focus was observed (41,79), two separate foci were detected in most G 1 cells in T. brucei, consistent with the diploidy of the SL RNA repeat locus (25,180). A single SL RNA transcription spot might be the consequence of pairing of the two alleles induced by active transcription (32).…”

Section: Extranucleolar Bodies In Trypanosomesmentioning

confidence: 59%

Cell Biology of the Trypanosome Genome

Daniels

Gull

Wickstead

2010

Microbiol Mol Biol Rev

113

103

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SUMMARY Trypanosomes are a group of protozoan eukaryotes, many of which are major parasites of humans and livestock. The genomes of trypanosomes and their modes of gene expression differ in several important aspects from those of other eukaryotic model organisms. Protein-coding genes are organized in large directional gene clusters on a genome-wide scale, and their polycistronic transcription is not generally regulated at initiation. Transcripts from these polycistrons are processed by global trans-splicing of pre-mRNA. Furthermore, in African trypanosomes, some protein-coding genes are transcribed by a multifunctional RNA polymerase I from a specialized extranucleolar compartment. The primary DNA sequence of the trypanosome genomes and their cellular organization have usually been treated as separate entities. However, it is becoming increasingly clear that in order to understand how a genome functions in a living cell, we will need to unravel how the one-dimensional genomic sequence and its trans-acting factors are arranged in the three-dimensional space of the eukaryotic nucleus. Understanding this cell biology of the genome will be crucial if we are to elucidate the genetic control mechanisms of parasitism. Here, we integrate the concepts of nuclear architecture, deduced largely from studies of yeast and mammalian nuclei, with recent developments in our knowledge of the trypanosome genome, gene expression, and nuclear organization. We also compare this nuclear organization to those in other systems in order to shed light on the evolution of nuclear architecture in eukaryotes.

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Section: Extranucleolar Bodies In Trypanosomesmentioning

confidence: 59%

Cell Biology of the Trypanosome Genome

Daniels

Gull

Wickstead

2010

Microbiol Mol Biol Rev

113

103

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“…4A). Also, in Leishmania tarentolae, the SL promoter was recently shown to be devoid of nucleosomes (33). Furthermore, transcription of rRNA and SL RNA has several common features, including both promoter sequence and transcription factors, indicating a partly similar pattern of regulation (34) that might also include nucleosome depletion.…”

Section: Acetylated Histones Are Not Associated With Promoters Of Higmentioning

confidence: 99%

Histone Acetylation and Methylation at Sites Initiating Divergent Polycistronic Transcription in Trypanosoma cruzi

Respuela

Ferella

Rada-Iglesias

et al. 2008

Journal of Biological Chemistry

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Trypanosomes are ancient eukaryotic parasites in which the protein-coding genes, organized in large polycistronic clusters on both strands, are transcribed from as yet unidentified promoters. In an effort to reveal transcriptional initiation sites, we examined the Trypanosoma cruzi genome for histone modification patterns shown to be linked to active genes in various organisms. Here, we show that acetylated and methylated histones were found to be enriched at strand switch regions of divergent gene arrays, not at convergent clusters or intra-and intergenic regions within clusters. The modified region showed a bimodular profile with two peaks centered over the 5-regions of the gene pair flanking the strand switch region. This pattern, which demarcates polycistronic transcription units originating from bidirectional initiation sites, is likely to be common in kinetoplastid parasites as well as in other organisms with polycistronic transcription. In contrast, no acetylation was found at promoters of the highly expressed rRNA and spliced leader genes or satellite DNA or at tested retrotransposonal elements. These results reveal, for the first time, the presence of specific epigenetic marks in T. cruzi with potential implications for transcriptional regulation; they indicate that both histone modifications and bidirectional transcription are evolutionarily conserved.

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“…(10,53). The significant divergence in the trypanosome TBP may indicate functional variation in its role in transcription (22,58). Specifically, the trypanosome protein lacks two of the four important phenylalanines that are responsible for bending the DNA on either side of the TATA box.…”

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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The promoter and transcribed regions of the Leishmania tarentolae spliced leader RNA gene array are devoid of nucleosomes

Cited by 23 publications

References 59 publications

Cell Biology of the Trypanosome Genome

Cell Biology of the Trypanosome Genome

Histone Acetylation and Methylation at Sites Initiating Divergent Polycistronic Transcription in Trypanosoma cruzi

RNA Polymerase Transcription Machinery in Trypanosomes

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