Short leader sequences may be transferred from small RNAs to pre-mature mRNAs by trans-splicing in Euglena.

Tessier, Luc-Henri; Keller, Mario; Chan, Raquel L.; Fournier, R. E. K.; Weil, Jacques-Henry; Imbault, P.

doi:10.1002/j.1460-2075.1991.tb07804.x

Cited by 167 publications

(100 citation statements)

References 31 publications

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“…In trypanosomes, all of the genes are organized into operons, and SL addition separates the resulting polycistronic mRNAs into individual species (5,36). It is not known whether any of the genes in euglenoids, the other unicellular eukaryotes that are known to carry out spliced leader addition (6,7), are organized into operons. In C. elegans, about 25% of the genes are organized into operons (37).…”

Section: Discussionmentioning

confidence: 99%

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Trans-spliced leader addition to mRNAs in a cnidarian

Stover

Steele

2001

Proc. Natl. Acad. Sci. U.S.A.

108

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Section: Discussionmentioning

confidence: 99%

“…To date, SL addition has been identified in three metazoan phyla (Nematoda, Platyhelminthes, and Chordata) (1)(2)(3)(4) and in one unicellular eukaryotic phylum (Sarcomastigophora) (3,(5)(6)(7). No evidence of SL addition has been detected in any intensively studied plants, fungi, insects, echinoderms, or vertebrates.…”

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confidence: 99%

Trans-spliced leader addition to mRNAs in a cnidarian

Stover

Steele

2001

Proc. Natl. Acad. Sci. U.S.A.

108

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“…7; reviewed in refs. 8 and 9), in Euglena (10), and in flatworms (11,12). In contrast to trypanosomes, in which only trans-splicing is present, the genes in the other organisms also contain cis-spliced introns.…”

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confidence: 97%

Operons and SL2 trans-splicing exist in nematodes outside the genus Caenorhabditis

Evans

Zorio

MacMorris

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

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The genomes of most eukaryotes are composed of genes arranged on the chromosomes without regard to function, with each gene transcribed from a promoter at its 5 end. However, the genome of the free-living nematode Caenorhabditis elegans contains numerous polycistronic clusters similar to bacterial operons in which the genes are transcribed sequentially from a single promoter at the 5 end of the cluster. The resulting polycistronic pre-mRNAs are processed into monocistronic mRNAs by conventional 3 end formation, cleavage, and polyadenylation, accompanied by trans-splicing with a specialized spliced leader (SL), SL2. To determine whether this mode of gene organization and expression, apparently unique among the animals, occurs in other species, we have investigated genes in a distantly related free-living rhabditid nematode in the genus Dolichorhabditis (strain CEW1). We have identified both SL1 and SL2 RNAs in this species. In addition, we have sequenced a Dolichorhabditis genomic region containing a gene cluster with all of the characteristics of the C. elegans operons. We show that the downstream gene is trans-spliced to SL2. We also present evidence that suggests that these two genes are also clustered in the C. elegans and Caenorhabditis briggsae genomes. Thus, it appears that the arrangement of genes in operons pre-dates the divergence of the genus Caenorhabditis from the other genera in the family Rhabditidae, and may be more widespread than is currently appreciated.In bacteria and archaea, the genomes are primarily organized in arrays of genes whose products have related functions. These gene clusters, called operons, are cotranscribed from an upstream promoter and the resulting polycistronic mRNA is translated by ribosomes initiating at or near the 5Ј end of the RNA. These operons serve to efficiently coregulate proteins that function together. In contrast, eukaryotes have genomes composed of genes arranged apparently at random, with each transcribed by a promoter at its 5Ј end. However, in a group of primitive eukaryotic protozoa, the trypanosomes, genes are transcribed polycistronically (1-3). In this case, the polycistronic pre-mRNA is processed by 3Ј end formation and trans-splicing to create conventional eukaryotic monocistronic mRNAs. The trans-splicing reaction that creates the 5Ј ends of the mRNAs is related to the cis-splicing of higher eukaryotes; it proceeds through a 2Ј-5Ј branched intermediate, the splice sites have the same consensus sequences, and it is catalyzed by some of the same small nuclear ribonucleoprotein particles (4, 5).Trans-splicing was first discovered in trypanosomatids (4, 6), and later shown to occur also in Caenorhabditis elegans and other nematodes (ref. 7; reviewed in refs. 8 and 9), in Euglena (10), and in flatworms (11,12). In contrast to trypanosomes, in which only trans-splicing is present, the genes in the other organisms also contain cis-spliced introns. It was presumed that these genes were monocistronic and arranged randomly on the chromosomes as in other...

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“…Although described at first in Kinetoplastida, SL trans-splicing was subsequently shown to occur in other protists of the Euglenozoa phylum, i.e. Euglenida (Tessier et al 1991, Ebel et al 1999, Frantz et al 2000, Diplonemida (Sturm et al 2001), and Kinetoplastida (Murphy et al 1986, Sutton & Boothroyd 1986, Laird et al 1987). In the metazoans, trans-splicing has been described in free-living or parasitic nematodes (Krause & Hirsh 1987, Blaxter & Liu 1996, in trematodes (Rajkovic et al 1990, Davis et al 1994) and cestodes (Brehm et al 2000) as well as in turbelarians (Davis 1997) of the Platyhelminthes phylum.…”

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Pre-mRNA trans-splicing: from kinetoplastids to mammals, an easy language for life diversity

Mayer

Flöeter-Winter²

2005

Mem. Inst. Oswaldo Cruz

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Since the discovery that genes are split into intron and exons, the studies of the mechanisms involved in splicing pointed to presence of consensus signals in an attempt to generalize the process for all living cells. However, as discussed in the present review, splicing is a theme full of variations. The trans-splicing of pre-mRNAs, the joining of exons from distinct transcripts, is one of these variations with broad distribution in the phylogenetic tree. The biological meaning of this phenomenon is discussed encompassing reactions resembling a possible noise to mechanisms of gene expression regulation. All of them however, can contribute to the generation of life diversity.Key words: RNA processing -alternative trans-splicing -spliced leader RNA -trypanosomatids -nematodes -mammalian Most of the protein-coding eukaryotic genes display an interrupted structure alternating exons and introns. After transcription, introns must be removed from the primary transcript (pre-mRNA) to generate a translatable mature mRNA. It is interesting to note that the mature mRNA is constituted of 5' and 3' untranslatable regions (UTR) flanking the open reading frame (ORF) and that UTR are also exons. The precise excision of the introns and the joining of neighboring exons is a complex process generally named splicing, and when this processing occurs within a single pre-mRNA molecule it can also be called cis-splicing (Moore et al. 1993, Burge et al. 1999.Cis-splicing occurs in a two-step mechanism, each step consisting of a transesterification reaction (Moore et al. 1993) (Fig. 1A). The spliceosome, a ribonucleoprotein machinery composed of five small ribonucleoproteins (U1, U2, U4, U5, U6 snRNPs, named in relation to the kind of associated RNA molecule) and approximately 300 distinct proteins, is responsible for the splicing catalysis (Burge et al. 1999).Much effort was expended on the comprehension of the structure and dynamics of this complex machine during the splicing process, but the rules that discriminate introns and exons within the message are still poorly understood. Nevertheless, four conserved pre-mRNA sequence elements, which interact with the spliceosome, have been characterized as determinants in the splicing process (Moore et al. 1993, Burge et al. 1999 (Fig. 1C). In mammals, the 5' splice site consensus is AG/GURAGU (R for purine, /for splice site, bold for the dinucleotide 5' intron boundary) while the 3' splice site consensus is YAG/G (Y for pyrimidine, /for splice site, bold for the dinucleotides 3' intron boundary). There is also a conservation of nucleotide sequence around the branch point, CURAY (Y for pyrimidine, R for purine and A for branch Recently, other cis-regulatory elements were implicated in splice site recognition, e.g. the exonic splicing enhancers (ESEs) (Fig. 1C). ESEs are localized within exons and interact with a family of proteins rich in serine and arginine (SR proteins) that recruits the spliceosome to the proximal splice site .Although the presence of those consensuses was observed, it i...

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Short leader sequences may be transferred from small RNAs to pre-mature mRNAs by trans-splicing in Euglena.

Cited by 167 publications

References 31 publications

Trans-spliced leader addition to mRNAs in a cnidarian

Trans-spliced leader addition to mRNAs in a cnidarian

Operons and SL2 trans-splicing exist in nematodes outside the genus Caenorhabditis

Pre-mRNA trans-splicing: from kinetoplastids to mammals, an easy language for life diversity

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