Search for promoters for the GARP and rRNA genes of Trypanosoma congolense

Downey, Nicholas; Donelson, John E.

doi:10.1016/s0166-6851(99)00135-8

Cited by 20 publications

(15 citation statements)

References 34 publications

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“…Putative promoters for actin (2), hsp70 (15), and GARP (11) genes have been reported in Trypanosoma brucei and Trypanosoma congolense, although these conclusions remain controversial (5,7,20). Until recently, the only Pol II promoter region that has been extensively characterized is the one driving the expression of the SL RNA (10).…”

Section: Discussionmentioning

confidence: 99%

Transcription Initiation and Termination on Leishmania major Chromosome 3

et al. 2004

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Genome projects involving Leishmania and other trypanosomatids have revealed that most genes in these organisms are organized into large clusters of genes on the same DNA strand. We have previously shown that transcription of the entire Leishmania major Friedlin (LmjF) chromosome 1 (chr1) initiates bidirectionally between two divergent gene clusters. Here, we analyze transcription of LmjF chr3, which contains two convergent clusters of 67 and 30 genes, separated by a tRNA gene, with a single divergent protein-coding gene located close to the "left" telomere. Nuclear run-on analyses indicate that specific transcription of chr3 initiates bidirectionally between the single subtelomeric gene and the adjacent 67-gene cluster, close to the "right" telomere upstream of the 30-gene cluster, and upstream of the tRNA gene. Transcription on both strands terminates within the tRNA-gene region. Transient-transfection studies support the role of the tRNA-gene region as a transcription terminator for RNA polymerase II (Pol II) and Pol III, and also for Pol I.Leishmania is a protozoan parasite (order Kinetoplastida) which alternates life-forms between an intracellular amastigote stage residing in vertebrate macrophages and an extracellular promastigote stage living in the digestive tract of sandflies. The numerous human-infective Leishmania species cause a spectrum of disease ranging from asymptomatic to lethal, resulting in widespread human suffering and death, as well as considerable economic loss (35).Leishmania, as well as other members of the Trypanosomatidae family, possesses unusual mechanisms of gene expression, such as polycistronic transcription (13,19) and RNA editing of the mitochondrial transcripts (37). In these organisms, the mature nuclear mRNAs are generated from primary transcripts by trans-splicing, a process that adds a capped 39-nucleotide (nt) miniexon or splice leader (SL) to the 5Ј termini of the mRNAs (27). The steady-state levels of most of the mature mRNAs appear to be regulated posttranscriptionally by mechanisms that involve their 3Ј untranslated region sequences (23). Promoters for RNA polymerase I (Pol I) have been extensively characterized in trypanosomatids (31,44,46), as have some Pol III promoters (3,26). However, little is known about the sequences that drive the expression of protein-coding genes by Pol II.The Leishmania haploid genome content is ϳ34 Mb, consisting of 36 chromosomes which range in size from 0.3 to 2.5 Mb (40). The Leishmania Genome Network was established with the support of the World Health Organization to map and sequence the genome of Leishmania major Friedlin (LmjF), the reference strain of the project. The sequence of chromosome 1 (chr1), the smallest in the parasite, revealed the presence of 79 putative genes, the first 29 of which are in a cluster on the "bottom" DNA strand, while the remaining 50 are in a cluster on the "top" strand (21). Importantly, nuclear run-on analysis of chr1 showed that specific transcription, leading to the production of stable transcripts, ...

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Section: Discussionmentioning

confidence: 99%

Transcription Initiation and Termination on Leishmania major Chromosome 3

et al. 2004

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“…On the other hand, the rRNA gene intergenic spacer region (IGS) and the external transcribed spacer (ETS) are under less selective pressure and thus provide a means to distinguish evolutionary relationships among more closely-related species. The IGS/ETS region of trypanosomatids have been widely studied (White et al 1986, Grondal et al 1990, Zomerdijk et al 1991, Rudenko et al 1991, Dietrich et al 1993, Martinez-Calvillo & Hernandez 1994, Tyler-Cross et al 1995, Uliana et al 1996, Gay et al 1996, Yan et al 1999, Downey & Donelson 1999, Schnare et al 2000 and shows a general organization similar to the majority of eukaryotes.…”

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confidence: 99%

Intergenic and external transcribed spacers of ribosomal RNA genes in lizard-infecting Leishmania: molecular structure and phylogenetic relationship to mammal-infecting Leishmania in the subgenus Leishmania (Leishmania)

Orlando

Rubio²,

Sturm³

et al. 2002

Mem. Inst. Oswaldo Cruz

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“…However, proving the existence of RNA polymerase II promoters for protein-coding genes is very elusive. Nevertheless, there are reports to support the existence of such promoters (44,45). However, in Leishmania and Leptomonas it is possible to obtain expression of a marker from episomes containing only the plasmid backbone; the marker gene is preceded by a splice acceptor and a synthetic polypyrimidine tract but with no obvious promoter (46,47).…”

Section: Discussionmentioning

confidence: 99%

Small Nucleolar RNA Clusters in Trypanosomatid Leptomonas collosoma

Liang

Ochaion

et al. 2004

Journal of Biological Chemistry

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Trypanosomatid small nucleolar RNA (snoRNA) genes are clustered in the genome. snoRNAs are transcribed polycistronically and processed into mature RNAs. In this study, we characterized four snoRNA clusters in Leptomonas collosoma. All of the clusters analyzed carry both C/D and H/ACA RNAs. The H/ACA RNAs are composed of a single hairpin, a structure typical to trypanosome and archaea guide RNAs. Using deletion and mutational analysis of a tagged C/D snoRNA situated within the snoRNA cluster, we identified 10-nucleotide flanking sequences that are essential for processing snoRNA from its precursor. Chromosome walk was performed on a snoRNA cluster, and a sequence of 700 bp was identified between the first repeat and the upstream open reading frame. Cloning of this sequence in an episome vector enhanced the expression of a tagged snoRNA gene in an orientation-dependent manner. However, continuous transcript spanning of this region was detected in steady-state RNA, suggesting that snoRNA transcription also originates from an upstreamlong polycistronic transcriptional unit. The 700-bp fragment may therefore represent an example of many more elements to be discovered that enhance transcription along the chromosome, especially when transcription from the upstream gene is reduced or when enhanced transcription is needed.In eukaryotes, pre-rRNA transcript undergoes numerous site-specific modifications before cleavage. Two prevalent modifications, 2Ј-O-methylation and conversion of uridine to pseudouridine, are guided by C/D box and H/ACA box small nucleolar RNAs (snoRNAs), 1 respectively (1-3). The C/D snoRNAs carry short conserved motives, as do the C box (RUG-AUGA) and D box (CUGA), near the 5Ј and 3Ј ends, respectively, as well as the internal DЈ and CЈ boxes. Sequences (Ͼ10 nt) upstream from the D and/or DЈ box can interact with the target RNA by perfect base pairing. The 5th nt on the target RNA upstream from the D or DЈ box in the duplex is methylated, which is known as the "ϩ5 rule" (1). The H/ACA snoRNAs that guide pseudouridylation carry two hairpin structures linked by the H box (AnAnnA) in the hinge region and an ACA box 3 nt upstream from the 3Ј end. The internal loop interacts with the target RNA to form the pseudouridylation pocket. The uridine on the target RNA to be isomerized is located usually 14 -16 nts upstream from the ACA and/or H box (2, 3).In vertebrates, all guide snoRNAs are intronic (4, 5). Most yeast snoRNAs are encoded by independent genes, some of which are found in clusters. However, seven intronic genes were also described (6). In plants, most snoRNAs are clustered and are independently transcribed, but intronic snoRNA gene clusters also exist (7-9). The intronic snoRNA genes are transcribed from the promoter of host genes by RNA polymerase II (10, 11). The polycistronic snoRNAs in yeast are transcribed by polymerase II from their own promoters carrying the TATA box and the binding site of Rap1p, a transcription factor involved in ribosomal protein expression (6). In plants, promoters exp...

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Search for promoters for the GARP and rRNA genes of Trypanosoma congolense

Cited by 20 publications

References 34 publications

Transcription Initiation and Termination on Leishmania major Chromosome 3

Transcription Initiation and Termination on Leishmania major Chromosome 3

Intergenic and external transcribed spacers of ribosomal RNA genes in lizard-infecting Leishmania: molecular structure and phylogenetic relationship to mammal-infecting Leishmania in the subgenus Leishmania (Leishmania)

Small Nucleolar RNA Clusters in Trypanosomatid Leptomonas collosoma

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