Intercistronic Region Required for Polycistronic Pre-mRNA Processing in <i>Caenorhabditis elegans</i>

Huang, Tao; Kuersten, Scott; Deshpande, Atul; Strouboulis, John; MacMorris, Margaret; Blumenthal, Thomas

doi:10.1128/mcb.21.4.1111-1120.2001

Cited by 57 publications

(67 citation statements)

References 23 publications

(14 reference statements)

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“…Polycistronic transcription in eukaryotes is very rare, and involvement of more than two genes is, to our knowledge, restricted to nematodes and trypanosomes, but the architecture and processing mechanism significantly differ from bacteria (26). In particular, neither cleavage and polyadenylationspecificity-factor binding sites nor U-rich elements required for trans splicing, which would be expected for eukaryotic premRNA processing (27), were found on the sequenced cosmid. These different lines of evidence therefore all point to a bacterium as the carrier of the PKS genes.…”

Section: Discussionmentioning

confidence: 99%

Antitumor polyketide biosynthesis by an uncultivated bacterial symbiont of the marine sponge Theonella swinhoei

Piel

Hui

Wen

et al. 2004

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

506

405

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Bacterial symbionts have long been suspected to be the true producers of many drug candidates isolated from marine invertebrates. Sponges, the most important marine source of biologically active natural products, have been frequently hypothesized to contain compounds of bacterial origin. This symbiont hypothesis, however, remained unproven because of a general inability to cultivate the suspected producers. However, we have recently identified an uncultured Pseudomonas sp. symbiont as the most likely producer of the defensive antitumor polyketide pederin in Paederus fuscipes beetles by cloning the putative biosynthesis genes. Here we report closely related genes isolated from the highly complex metagenome of the marine sponge Theonella swinhoei, which is the source of the onnamides and theopederins, a group of polyketides that structurally resemble pederin. Sequence features of the isolated genes clearly indicate that it belongs to a prokaryotic genome and should be responsible for the biosynthesis of almost the entire portion of the polyketide structure that is correlated with antitumor activity. Besides providing further proof for the role of the related beetle symbiont-derived genes, these findings raise intriguing ecological and evolutionary questions and have important general implications for the sustainable production of otherwise inaccessible marine drugs by using biotechnological strategies. F or almost 30 years, symbiotic bacteria have been discussed as the likely true producers of numerous natural products isolated from marine invertebrates (1). Particularly suggestive of a bacterial origin is the similarity of many compounds from sponges, tunicates, or bryozoans to complex polyketides and nonribosomal peptides, two groups of metabolites that are otherwise known exclusively from microorganisms (2, 3). Into these structural families fall some of today's most promising drug candidates, such as discodermolide, bryostatin 1, aplidine, and ET-743 (4). The existence of producing symbionts could have far reaching consequences for the development of sustainable, fermentation-based sources of invertebrate-derived drug candidates, almost all of which are currently inaccessible in large amounts. Several studies have tried to pinpoint the producers by using cultivation (5), cell separation (6), immunolocalization (7), or in situ hybridization (8) approaches. However, as none of these methods have so far provided unambiguous results, the true origin of the compounds still remains an enigma. We have recently used a genetic strategy to provide insights into natural product symbiosis in terrestrial insects (9). Rove beetles of the genera Paederus and Paederidus are the source of the highly active antitumor polyketide pederin (Fig. 1), which they use as chemical defense (10). We isolated a set of putative pederin biosynthesis genes (9, 11) from the metagenome of Paederus fuscipes beetles and traced them to a bacterial symbiont with the closest relationship to Pseudomonas aeruginosa (12). The genes encode a mixed modul...

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Section: Discussionmentioning

confidence: 99%

Antitumor polyketide biosynthesis by an uncultivated bacterial symbiont of the marine sponge Theonella swinhoei

Piel

Hui

Wen

et al. 2004

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

506

405

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“…Furthermore, a conserved U-rich element localized in the intercistronic region of several C. elegans and Caenorhabditis briggsae operons has been recently identified (54). Mutational analysis has shown the U-rich element is essential for pre-mRNA processing of genes within a C. elegans operon (54). A U-rich RNA-binding protein, TcUBP-1, has also recently been identified in Trypansoma cruzi.…”

Section: Discussionmentioning

confidence: 99%

“…As pre-mRNA, GU repeats have the potential to form stable hairpin-loop structures that could interact with regulatory factors involved in 3Ј-end processing and are themselves developmentally regulated (53). Furthermore, a conserved U-rich element localized in the intercistronic region of several C. elegans and Caenorhabditis briggsae operons has been recently identified (54). Mutational analysis has shown the U-rich element is essential for pre-mRNA processing of genes within a C. elegans operon (54).…”

Section: Discussionmentioning

confidence: 99%

The Stage-regulated Expression of Leishmania mexicanaCPB Cysteine Proteases Is Mediated by an Intercistronic Sequence Element

Brooks

Denise

Westrop³

et al. 2001

Journal of Biological Chemistry

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The tandemly arranged CPB genes of Leishmania mexicana are polycistronically transcribed and encode cysteine proteases that are differentially stage-specific; CPB1 and CPB2 are expressed predominantly in metacyclics, whereas CPB3-CPB18 are expressed mainly in amastigotes. The mechanisms responsible for this differential expression have been studied via gene analysis and re-integration of individual CPB genes, and variants thereof, into a CPB-deficient parasite mutant. Comparison of the nucleotide sequences of the repeat units of CPB1 and CPB2 with CPB2.8 (typical of CPB3-CPB18) revealed two major regions of divergence as follows: one of 258 base pairs (bp) corresponding to the C-terminal extension of CPB2.8; another, designated InS, of 120 bp, with insertions totaling 57 bp, localized to the intercistronic region downstream of CPB1 and CPB2. Cell lines expressing CPB2.8 or CPB2 with the 3-untranslated region and intercistronic sequence of CPB2.8 showed upregulation in amastigotes. Conversely, metacyclic-specific expression occurred with CPB2 or CPB2.8 with the 3-untranslated region and intercistronic sequence of CPB2. Moreover, the InS down-regulated expression in amastigotes of a reporter gene integrated into the CPB locus. It is proposed that the InS mediates metacyclicspecific stage-regulated expression of CPB by affecting the maturation of polycistronic pre-mRNA. This is the first well defined cis-regulatory element implicated in post-transcriptional stage-specific gene expression in Leishmania.

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“…The che-12 and dyf-11 cDNAs were inserted downstream of a 2.4-kb promoter region of the gene sra-6 (Troemel et al 1995) as XmaI/SacI and NgoMIV/XmaI fragments, respectively. To make dual-expression constructs, the che-12 and dyf-11 cDNAs were inserted downstream of the SL2 acceptor sequence (Huang et al 2001) in the vector gcy-5 proTmCherryTSL2 acceptor siteTGFP.…”

Section: Methodsmentioning

confidence: 99%

The Conserved Proteins CHE-12 and DYF-11 Are Required for Sensory Cilium Function in Caenorhabditis elegans

Bacaj

Shaham

2008

Genetics

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Sensory neuron cilia are evolutionarily conserved dendritic appendages that convert environmental stimuli into neuronal activity. Although several cilia components are known, the functions of many remain uncharacterized. Furthermore, the basis of morphological and functional differences between cilia remains largely unexplored. To understand the molecular basis of cilia morphogenesis and function, we studied the Caenorhabditis elegans mutants che-12 and dyf-11. These mutants fail to concentrate lipophilic dyes from their surroundings in sensory neurons and are chemotaxis defective. In che-12 mutants, sensory neuron cilia lack distal segments, while in dyf-11 animals, medial and distal segments are absent. CHE-12 and DYF-11 are conserved ciliary proteins that function cell-autonomously and are continuously required for maintenance of cilium morphology and function. CHE-12, composed primarily of HEAT repeats, may not be part of the intraflagellar transport (IFT) complex and is not required for the localization of some IFT components. DYF-11 undergoes IFT-like movement and may function at an early stage of IFT-B particle assembly. Intriguingly, while DYF-11 is expressed in all C. elegans ciliated neurons, CHE-12 expression is restricted to some amphid sensory neurons, suggesting a specific role in these neurons. Our results provide insight into general and neuron-specific aspects of cilium development and function.

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Intercistronic Region Required for Polycistronic Pre-mRNA Processing in Caenorhabditis elegans

Cited by 57 publications

References 23 publications

Antitumor polyketide biosynthesis by an uncultivated bacterial symbiont of the marine sponge Theonella swinhoei

Antitumor polyketide biosynthesis by an uncultivated bacterial symbiont of the marine sponge Theonella swinhoei

The Stage-regulated Expression of Leishmania mexicanaCPB Cysteine Proteases Is Mediated by an Intercistronic Sequence Element

The Conserved Proteins CHE-12 and DYF-11 Are Required for Sensory Cilium Function in Caenorhabditis elegans

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