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Amplification of siRNA in Caenorhabditis elegans generates a transgenerational sequence-targeted histone H3 lysine 9 methylation footprint

ABSTRACT: Exogenous double-stranded RNA (dsRNA) has been shown to exert homology-dependent effects at the level of both target mRNA stability and chromatin structure. Using C. elegans undergoing RNAi as an animal model, we have investigated the generality, scope, and longevity of chromatin-targeted dsRNA effects and their dependence on components of the RNAi machinery. Using high-resolution genome-wide chromatin profiling, we found that a diverse set of genes can be induced to acquire locus-specific enrichment of H3K9 trimethylation, with modification footprints extending several kilobases from the site of dsRNA homology and with locus specificity sufficient to distinguish the targeted locus from among all 20,000 genes in the C. elegans genome. Genetic analysis of the response indicated that factors responsible for secondary siRNA production during RNAi were required for effective targeting of chromatin. Temporal analysis revealed that H3K9 methylation, once triggered by dsRNA, can be maintained in the absence of dsRNA for at least two generations before being lost. These results implicate dsRNA-triggered chromatin modification in C. elegans as a programmable and locus-specific response defining a metastable state that can persist through generational boundaries.

ORGANISM(S): Caenorhabditis elegans

PROVIDER: GSE32631 | GEO | 2012/01/06

SECONDARY ACCESSION(S): PRJNA146973

REPOSITORIES: GEO

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Amplification of siRNA in Caenorhabditis elegans generates a transgenerational sequence-targeted histone H3 lysine 9 methylation footprint

Project description:Exogenous double-stranded RNA (dsRNA) has been shown to exert homology-dependent effects at the level of both target mRNA stability and chromatin structure. Using C. elegans undergoing RNAi as an animal model, we have investigated the generality, scope, and longevity of chromatin-targeted dsRNA effects and their dependence on components of the RNAi machinery. Using high-resolution genome-wide chromatin profiling, we found that a diverse set of genes can be induced to acquire locus-specific enrichment of H3K9 trimethylation, with modification footprints extending several kilobases from the site of dsRNA homology and with locus specificity sufficient to distinguish the targeted locus from among all 20,000 genes in the C. elegans genome. Genetic analysis of the response indicated that factors responsible for secondary siRNA production during RNAi were required for effective targeting of chromatin. Temporal analysis revealed that H3K9 methylation, once triggered by dsRNA, can be maintained in the absence of dsRNA for at least two generations before being lost. These results implicate dsRNA-triggered chromatin modification in C. elegans as a programmable and locus-specific response defining a metastable state that can persist through generational boundaries. H3K9me3 nucleosome-IP sequencing and small RNA sequencing in C. elegans populations that underwent RNAi

2012-01-06 | E-GEOD-32631 | biostudies-arrayexpress

Decoupling the downstream effects of germline nuclear RNAi reveals that transcriptional repression and heritable RNAi are independent of the H3K9me3 response in C. elegans [pre-mRNA-seq]

Project description:Germline nuclear RNAi in C. elegans is a transgenerational gene-silencing pathway that leads to the H3K9 trimethylation (H3K9me3) response and transcriptional repression of target genes. The H3K9me3 response induced either by exogenous dsRNA or endogenous siRNA (endo-siRNA) is highly specific to the target loci and transgenerationally heritable. Despite these features, the role of H3K9me3 in transcriptional repression and heritable gene silencing at native target genes has not been tested. To resolve this gap, we first determined that the combined activities of three H3K9 histone methyltransferases (HMTs), MET-2, SET-25, and SET-32, are responsible for virtually all of the detectable level of germline nuclear RNAi-dependent H3K9me3 at native genes, triggered either by exogenous dsRNA or endo-siRNAs. By performing RNA Polymerase II ChIP-seq and pre-mRNA-seq analyses, we found that the loss of the H3K9me3 response at germline nuclear RNAi targets in the met-2;set-25;set-32 mutant does not lead to any defect in transcriptional repression or heritable RNAi. Therefore, H3K9me3 is not required for exogenous dsRNA-induced heritable RNAi or the maintenance of endo siRNA-mediated transcriptional silencing in C. elegans germline. This study provides a unique paradigm in which transcriptional silencing and heterochromatin, triggered by the same upstream pathway, can be decoupled.

2017-01-01 | GSE86516 | GEO

Decoupling the downstream effects of germline nuclear RNAi reveals that transcriptional repression and heritable RNAi are independent of the H3K9me3 response in C. elegans [RNA-seq]

2017-01-01 | GSE86515 | GEO

Decoupling the downstream effects of germline nuclear RNAi reveals that transcriptional repression and heritable RNAi are independent of the H3K9me3 response in C. elegans [ChIP-seq]

2017-01-01 | GSE86513 | GEO

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

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

2006-11-17 | GSE6282 | 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

Effects of dsRNA-GFP as exogenous control on honey bee RNAi assays: gene expression changes in workers

Project description:A green fluorescence protein (GFP)-derived dsRNA (dsRNA-GFP) has been used as an exogenous control for Apis mellifera RNAi assays by multiple research groups. Its sequence does not share any significant homology with any known honey bee genes. Although dsRNA-GFP is not expected to trigger an RNAi response in treated bees, undesirable effects on gene expression, pupal pigmentation or developmental timing have been routinely observed. To better understand the multiple molecular and phenotypic effects of dsRNA-GFP in honey bees and to evaluate its use as a control for RNAi studies, we examined the impact of dsRNA-GFP on global gene expression patterns in developing workers. We found that dsRNA-GFP causes large-scale changes in gene expression associated with multiple biological processes. Furthermore, dsRNA-GFP exposure tended to preferentially decrease, rather than increase, expression of genes compared to controls.

2013-01-10 | GSE41004 | GEO

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.

2012-07-30 | GSE38041 | GEO

A nuclear Argonaute promotes germline immortality and epigenetic inheritance across generations

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

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