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C. elegans small RNA sequences from wild type animals fed on sel-1 dsRNA producing bacteria

ABSTRACT: RNA interference (RNAi) is a phylogenetically widespread gene silencing process triggered by doublestranded RNA (dsRNA). In plants and C. elegans, two distinct populations of small RNAs have been proposed to participate in RNAi : "Primary siRNAs" (derived from Dicer nuclease-mediated cleavage of the original trigger) and "Secondary siRNAs" (additional small RNAs whose synthesis requires an RNA-directed RNA polymerase [RdRP]). Analyzing small RNAs associated with ongoing RNAi in C. elegans, we found secondary siRNAs to comprise the vast majority. The bulk of secondary siRNAs exhibited structure and sequence indicative of a biosynthetic mode where each molecule derives from an independent de novo initiation by RdRP. Analysis of endogenous small RNAs indicated that a fraction derive from a biosynthetic mechanism that is similar to that of secondary siRNAs formed during RNAi, suggesting that small antisense transcripts derived from cellular mRNAs by RdRP activity may have key roles in cellular regulation. Keywords: C. elegans small RNA sequences from wild type animals fed on sel-1 dsRNA producing bacteria

ORGANISM(S): Caenorhabditis elegans

PROVIDER: GSE6282 | GEO | 2006/11/17

SECONDARY ACCESSION(S): PRJNA99679

REPOSITORIES: GEO

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C. elegans small RNA sequences from wild type animals fed on sel-1 dsRNA producing bacteria

Project description:RNA interference (RNAi) is a phylogenetically widespread gene silencing process triggered by doublestranded RNA (dsRNA). In plants and C. elegans, two distinct populations of small RNAs have been proposed to participate in RNAi : "Primary siRNAs" (derived from Dicer nuclease-mediated cleavage of the original trigger) and "Secondary siRNAs" (additional small RNAs whose synthesis requires an RNA-directed RNA polymerase [RdRP]). Analyzing small RNAs associated with ongoing RNAi in C. elegans, we found secondary siRNAs to comprise the vast majority. The bulk of secondary siRNAs exhibited structure and sequence indicative of a biosynthetic mode where each molecule derives from an independent de novo initiation by RdRP. Analysis of endogenous small RNAs indicated that a fraction derive from a biosynthetic mechanism that is similar to that of secondary siRNAs formed during RNAi, suggesting that small antisense transcripts derived from cellular mRNAs by RdRP activity may have key roles in cellular regulation. Keywords: C. elegans small RNA sequences from wild type animals fed on sel-1 dsRNA producing bacteria C. elegans small RNA sequences from wild type animals fed on sel-1 dsRNA producing bacteria

2006-11-17 | E-GEOD-6282 | biostudies-arrayexpress

The interplay between small RNA pathways shapes chromatin landscapes in C. elegans

Project description:The nematode C. elegans contains several types of endogenous small interfering RNAs (endo-siRNAs) produced by RNA-dependent RNA polymerase (RdRP) complexes. Both “silencing” siRNAs bound by Worm-specific Argonautes (WAGO) and “activating” siRNAs bound by the CSR-1 Argonaute require the DRH-3 helicase, an RdRP component. Here we show that, in the drh-3(ne4253) mutant deficient in RdRP-produced secondary endo-siRNAs, the silencing histone mark H3K9me3 is largely depleted, whereas in the csr-1 partial loss-of-function mutant this mark is ectopically deposited on CSR-1 target genes. Moreover, we observe ectopic H3K9me3 at enhancer elements in both drh-3 and csr-1 partial loss-of-function mutants and describe small RNAs matching enhancers. Finally, we detect accumulation of H3K27me3 at highly expressed genes in the drh-3(ne4253) mutant, which correlates with their reduced transcription. Our study shows that when abundant RdRP-produced siRNAs are depleted, there is ectopic elevation of noncoding RNAs linked to increase in silencing chromatin marks. Moreover, our results suggest that enhancer small RNAs may guide local H3K9 methylation.

2019-04-04 | GSE115629 | GEO

A Ribonuclease Coordinates siRNA Amplification and mRNA Cleavage during RNAi

Project description:Effective silencing by RNA-interference (RNAi) depends on mechanisms that amplify and propagate the silencing signal. In some organisms, small-interfering (si) RNAs are amplified from target mRNAs by RNA-dependent RNA polymerase (RdRP). Both RdRP recruitment and mRNA silencing require Argonaute proteins, which are generally thought to degrade RNAi targets by directly cleaving them. However in C. elegans, the enzymatic activity of the primary Argonaute, RDE-1, is not required for silencing activity. We show that RDE-1 can instead recruit an endoribonuclease, RDE-8, to target RNA. RDE-8 can cleave RNA in vitro and is needed for the production of 3′ uridylated fragments of target mRNA in vivo. We also find that RDE-8 promotes RdRP activity, thereby ensuring amplification of siRNAs. Together, our findings suggest a model in which RDE-8 cleaves target mRNAs to mediate silencing, while generating 3’ uridylated mRNA fragments to serve as templates for the RdRP-directed amplification of the silencing signal. We examined the role of rde-8 in C. elegans small RNA biogenesis pathways, including endogenous and exogenous RNAi pathways. We performed 3' RACE seq from the sel-1 target mRNA and correlate with small RNAs from wild type, rde-8 and rde-8 transgenic strains after sel-1(RNAi) for different lengths of time.

2015-01-29 | E-GEOD-59300 | biostudies-arrayexpress

High-pressure sprayed siRNAs influence the efficiency but not the profile of transitive silencing

Project description:In plants, small interfering RNAs (siRNAs) are a quintessential class of RNA interference (RNAi)-inducing molecules produced by the endonucleolytic cleavage of double stranded RNAs (dsRNAs). In order to ensure robust RNAi, siRNAs are amplified through a positive feedback mechanism called transitivity. Transitivity relies on RNA-DIRECTED-RNA POLYMERASE 6 (RDR6)-mediated dsRNA synthesis using siRNA-targeted RNA. The newly synthesized dsRNA is subsequently cleaved into secondary siRNAs by DICER-LIKE (DCL) endonucleases. Just like primary siRNAs, secondary siRNAs are also loaded into ARGONAUTE proteins (AGOs) to form an RNA-induced silencing complex (RISC) reinforcing the cleavage of the target RNA. Although the molecular players underlying transitivity are well established, the mode of action of transitivity remains elusive. In this study, we investigated the influence of primary target sites on transgene silencing and transitivity using the GFP-expressing Nicotiana benthamiana 16C line, high pressure spraying protocol (HPSP), and synthetic 22-nucleotide (nt) long siRNAs. We found that the 22-nt siRNA targeting the 3’ of the GFP transgene was less efficient in inducing silencing when compared to the siRNAs targeting the 5’ and middle region of the GFP. Moreover, sRNA sequencing of locally silenced leaves showed that the amount but not the profile of secondary RNAs is shaped by the occupancy of the primary siRNA triggers on the target RNA. Our findings suggest that RDR6-mediated dsRNA synthesis is not primed by primary siRNAs and that dsRNA synthesis appears to be generally initiated at the 3’ end of the target RNA.

2021-12-01 | GSE189777 | GEO

Proteins that interact physically with Drosophila blanks

Project description:RNA interference targets aberrant transcripts with cognate small interfering RNAs, which derive from double-stranded RNA precursors through nucleolytic processing. Several functional screens have identified Drosophila blanks/lump (CG10630) as a facilitator of RNAi in cultured cells, yet its molecular function has remained unknown. The protein carries two dsRNA binding domains (dsRBD) and blanks mutant males have a spermatogenesis defect. We demonstrate that blanks selectively boosts RNAi triggered by dsRNA of nuclear origin. Blanks binds dsRNA in vitro, shuttles between nucleus and cytoplasm and the abundance of certain endogenous siRNAs is reduced in blanks mutant testes. Transgenic expression of a Blanks protein variant with increased nuclear retention reduces endogenous siRNA abundance unless the protein also carries a mutation that prevents binding of dsRNA to the second dsRBD. Blanks thus facilitates the export of dsRNA to the cytoplasm for further processing by the canonical RNAi machinery. In contrast, rescue of male fertility in blanks mutant animals was independent of RNA binding to the second dsRBD, consistent with a previous report that linked fertility to the first dsRBD of Blanks. The role of blanks in spermatogenesis appears thus unrelated to its role in dsRNA export.

2020-05-26 | PXD013792 | Pride

A Ribonuclease Coordinates siRNA Amplification and mRNA Cleavage during RNAi

2015-01-29 | GSE59300 | GEO

Effects of ADARs on small RNA processing pathways in C. elegans

Project description:Adenosine deaminases that act on RNA (ADARs) are RNA editing enzymes that convert adenosine to inosine in double-stranded RNA (dsRNA). To evaluate effects of ADARs on small RNAs that derive from dsRNA precursors, we performed deep-sequencing, comparing small RNAs from wildtype and ADAR mutant C. elegans. While editing in small RNAs was rare, at least 40% of microRNAs had altered levels in at least one ADAR mutant strain, and miRNAs with significantly altered levels had mRNA targets with correspondingly affected levels. About 40% of siRNAs derived from endogenous genes (endo-siRNAs) also had altered levels in at least one mutant strain, including 63% of Dicer-dependent endo-siRNAs. The 26G class of endo-siRNAs was significantly affected by ADARs, and many altered 26G loci had intronic reads, and histone modifications associated with transcriptional silencing. Our data indicate ADARs, through both direct and indirect mechanisms, are important for maintaining wildtype levels of many small RNAs in C. elegans.

2012-04-05 | GSE28888 | GEO

Distinct phases of siRNA synthesis in an endogenous RNAi pathway in C. elegans soma

Project description:Endogenous RNA-directed RNA polymerases (RdRPs) are cellular components capable of synthesizing new complementary RNAs from existing RNA templates. We present evidence for successive engagement of two different RdRPs in an endogenous siRNA-based mechanism targeting specific mRNAs in C. elegans soma. In the initiation stage of this process, a group of mRNA species are chosen as targets for downregulation, leading to accumulation of rare 26-nt 5'-phosphorylated antisense RNAs that depend on the RdRP homolog RRF-3, the argonaute ERGO-1, DICER, and a series of associated (ERI) factors. This primary process leads to production of a much more abundant class of 22-nt antisense RNAs, dependent on a secondary RdRP (RRF-1) and associating with at least one distinct Argonaute (NRDE-3). The requirement for two RdRP/Argonaute combinations and initiation by a rare class of uniquely-structured siRNAs in this pathway illustrate the caution and flexibility used as biological systems exploit the physiological copying of RNA. 24 small RNA and 2 polyA RNA samples

2010-02-01 | E-GEOD-19414 | biostudies-arrayexpress

A nuclear Argonaute promotes germline immortality and epigenetic inheritance across generations

Project description:dsRNA-mediated gene silencing (RNAi) can be inherited for multiple generations in C. elegans. To understand this process we conducted a genetic screen for animals defective for transmitting RNAi silencing signals to future generations. This screen identified the gene heritable RNAi defective (hrde)-1. hrde-1 encodes an Argonaute (Ago) that associates with siRNAs in germ cells of the progeny of animals exposed to dsRNA. In nuclei of these germ cells, HRDE-1 engages the Nrde nuclear RNAi pathway to promote RNAi inheritance, and directs H3K9me3 chromatin marks at RNAi targeted genomic loci. Under normal growth conditions, HRDE-1 associates with endogenously expressed small RNAs, which direct nuclear gene silencing in germ cells. In RNAi inheritance mutant animals, silencing is lost over generational time. Concurrently, RNAi inheritance mutant animals exhibit progressively worsening germline defects that ultimately lead to sterility. These results establish that the Ago HRDE-1 directs gene-silencing events in germ cell nuclei, which are required for multi-generational RNAi inheritance and immortality of the germ cell lineage. We propose that C. elegans use the RNAi inheritance machinery to transmit epigenetic information, accrued by past generations, into future generations to ensure immortality of the germ cell lineage. H3K9me3 Chip-IP for C. elegans strains nrde-3, nrde-4, glp-4. Small RNA-seq for small RNAs co-immunoprecipitated with HRDE-1

2012-07-30 | E-GEOD-38041 | biostudies-arrayexpress

The RIG-I like receptor LGP2 inhibits Dicer-dependent processing of long double-stranded RNA and blocks RNA interference in mammalian cells.

Project description:In vertebrates, the presence of viral RNA in the cytosol is sensed by members of the RIG-I like receptor (RLR) family , which signal to induce production of type I interferons (IFN). These key anti-viral cytokines act in a paracrine and autocrine manner to induce hundreds of interferon-stimulated genes (ISGs), whose protein products restrict viral entry, replication and budding. ISGs include the RLRs themselves: RIG-I, MDA5 and the least-studied family member, LGP2. In contrast, the IFN system is absent in plants and invertebrates, which defend themselves from viral intruders using RNA interference (RNAi). In RNAi, the endoribonuclease Dicer cleaves virus-derived double stranded RNA (dsRNA) into small interfering RNAs (siRNAs) that target complementary viral RNA for cleavage. Interestingly, the RNAi machinery is conserved in mammals and we have recently demonstrated that it is able to participate in mammalian antiviral defence in conditions in which the IFN system is suppressed. In contrast, when the IFN system is active, one or more ISGs act to mask or suppress antiviral RNAi. Here, we demonstrate that LGP2 constitutes one of the ISGs that can inhibit antiviral RNAi in mammals. We identify Dicer as an LGP2-associated protein and show that LGP2 inhibits Dicer cleavage of dsRNA into siRNAs both in vitro and in vivo. Further, we show that in cells lacking an IFN response, ectopic expression of LGP2 interferes with RNAi-dependent suppression of gene expression. Thus, the inefficiency of RNAi as a mechanism of antiviral defence in mammalian somatic cells can be in part attributed to Dicer inhibition by LGP2 induced by type I IFNs.

2018-01-17 | PXD008364 | Pride

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