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Analysis of 22G siRNA triggered siRNA amplification and 3' 2'-O-methylated small RNAs in Caenorhabditis elegans

ABSTRACT: Small RNAs, including piRNAs, miRNAs and endogenous siRNAs, bind Argonaute proteins to form RNA-silencing complexes that target coding genes, transposons and aberrant RNAs. To assess the requirements for endogenous siRNA formation and activity in C. elegans, we developed a GFP-based sensor for the endogenous siRNA 22G siR-1, one of a set of abundant siRNAs processed from a precursor RNA mapping to the X chromosome, the X-cluster. Silencing of the sensor is also dependent on the partially complementary, unlinked 26G siR-O7 siRNA. We show that 26G siR-O7 acts in trans to initiate 22G siRNA formation from the X-cluster. The presence of several mispairs between 26G siR-O7 and the X-cluster mRNA, as well as mutagenesis of the siRNA sensor, indicates that siRNA target recognition is permissive to a degree of mispairing. From a candidate reverse genetic screen, we identified several factors required for 22G siR-1 activity, including the Argonaute ergo-1 and the 3' methyltransferase henn-1. Quantitative RT-PCR of small RNAs in a henn-1 mutant and deep sequencing of methylated small RNAs indicate that siRNAs and piRNAs that associate with PIWI clade Argonautes are methylated by HENN-1, while siRNAs and miRNAs that associate with non-PIWI clade Argonautes are not. Thus, PIWI-class Argonaute proteins are specifically adapted to associate with methylated small RNAs in C. elegans. This SuperSeries is composed of the SubSeries listed below.

ORGANISM(S): Caenorhabditis elegans

PROVIDER: GSE35550 | GEO | 2012/02/03

SECONDARY ACCESSION(S): PRJNA152667

REPOSITORIES: GEO

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Analysis of 22G siRNA triggered siRNA amplification and 3' 2'-O-methylated small RNAs in Caenorhabditis elegans

Project description:Small RNAs, including piRNAs, miRNAs and endogenous siRNAs, bind Argonaute proteins to form RNA-silencing complexes that target coding genes, transposons and aberrant RNAs. To assess the requirements for endogenous siRNA formation and activity in C. elegans, we developed a GFP-based sensor for the endogenous siRNA 22G siR-1, one of a set of abundant siRNAs processed from a precursor RNA mapping to the X chromosome, the X-cluster. Silencing of the sensor is also dependent on the partially complementary, unlinked 26G siR-O7 siRNA. We show that 26G siR-O7 acts in trans to initiate 22G siRNA formation from the X-cluster. The presence of several mispairs between 26G siR-O7 and the X-cluster mRNA, as well as mutagenesis of the siRNA sensor, indicates that siRNA target recognition is permissive to a degree of mispairing. From a candidate reverse genetic screen, we identified several factors required for 22G siR-1 activity, including the Argonaute ergo-1 and the 3' methyltransferase henn-1. Quantitative RT-PCR of small RNAs in a henn-1 mutant and deep sequencing of methylated small RNAs indicate that siRNAs and piRNAs that associate with PIWI clade Argonautes are methylated by HENN-1, while siRNAs and miRNAs that associate with non-PIWI clade Argonautes are not. Thus, PIWI-class Argonaute proteins are specifically adapted to associate with methylated small RNAs in C. elegans. This SuperSeries is composed of the following subset Series: GSE34320: Analysis of 22G siRNA triggered siRNA amplification in Caenorhabditis elegans GSE34321: Analysis of 3' 2'-O-methylated small RNAs in Caenorhabditis elegans Refer to individual Series

2012-02-03 | E-GEOD-35550 | biostudies-arrayexpress

The surveillance of pre-mRNA splicing is an early step in C. elegans RNA interference of endogenous genes.

Project description:Here we examine the role of mRNA splicing in Caenorhabditis elegans RNAi. We find that viable null mutations in U1 and U2-snRNP-specific splicing factor genes cause defects in RNAi. The U1A orthologue rnp-2 is required for normal ERGO-1 Argonaute-class 26G siRNA biogenesis, trans-splicing of the eri-6/7 transcript and targeting of poorly conserved gene transcripts by WAGO Argonaute-class 22G siRNAs. We find that poorly spliced gene transcripts engaged by the siRNA generating machinery are poorly conserved, possess few introns, and often have introns that are divergent from introns found in highly conserved genes.

2018-05-28 | GSE113301 | GEO

GTSF-1 is required for the formation of an RNA-dependent RNA Polymerase complex in C. elegans

Project description:In every domain of life, Argonaute proteins and their associated small RNAs regulate gene expression. Despite great conservation of Argonaute proteins throughout evolution, there are not many other conserved proteins involved in small RNA pathways. Gametocyte-specific factor 1 (Gtsf1) proteins, characterized by two tandem CHHC zinc fingers and an unstructured, acidic C-terminal tail, represent one such conserved small RNA pathway component. In fly and mouse, they are required for fertility and have been shown to interact with Piwi clade Argonautes. We identified T06A10.3 as the Caenorhabditis elegans Gtsf1 homolog and named it gtsf-1. Given its conserved nature and roles in Piwi-mediated gene silencing, we sought out to characterize GTSF-1 in the context of the small RNA pathways of C. elegans. Like its homologs, GTSF-1 is required for normal fertility. Surprisingly, we report that GTSF-1 is not required for Piwi-mediated gene silencing. Instead, gtsf-1 mutants lack a class of endogenous small RNAs, known as 26G-RNAs, and fully phenocopy mutants lacking RRF-3, the RNA-dependent RNA Polymerase that synthesizes 26G-RNAs. We show, both in vivo and in vitro, that GTSF-1 specifically and robustly interacts with RRF-3 via its tandem CHHC zinc fingers. Furthermore, we demonstrate that GTSF-1 is required for the assembly of a larger RRF-3 and DCR-1-containing complex, also known as ERIC, thereby allowing for 26G-RNA generation. We propose that GTSF-1 homologs may similarly act to drive the assembly of larger complexes that subsequently act in small RNA production and/or in imposing small RNA-mediated silencing activities.

2018-05-11 | PXD007665 | Pride

Analysis of 22G siRNA triggered siRNA amplification in Caenorhabditis elegans

Project description:To determine if an endogenous 22G siRNA sensor transgene is subject to siRNA amplification, small RNAs were deep sequenced from the sensor and from a control transgene that is identical to the sensor but lacks an siRNA target site.

2011-12-10 | GSE34320 | GEO

Analysis of 22G siRNA triggered siRNA amplification in Caenorhabditis elegans

2011-12-10 | E-GEOD-34320 | biostudies-arrayexpress

High throughput sequencing of mutants in the WAGO pathway

Project description:Diverse naturally-occurring small RNA species interact with Argonaute proteins to mediate sequence-specific regulation in animals. In addition to micro-RNAs (miRNAs), which collectively regulate thousands of target mRNAs, other endogenous small RNA species include the Piwi-associated piRNAs that are important for fertility and a less well-characterized class of small RNAs often referred to simply as endo-siRNAs. Here we have utilized deep-sequencing technology and C. elegans genetics to explore the biogenesis and function of endo-siRNAs. We describe conditional alleles of the dicer-related helicase, drh-3, that implicate DRH-3 in both the response to foreign dsRNA as well as the RNA-dependent RNA Polymerase (RdRP)-dependent biogenesis of a diverse class of endogenous small RNAs, termed 22G-RNAs. We show that 22G-RNAs are abundantly expressed in the germline and maternally inherited and are the products of at least two distinct 22G-RNA systems. One system is dependent on worm-specific AGOs, including WAGO-1, which localizes to germline nuage-related structures termed P-granules. The WAGO 22G-RNA system silences transposons, pseudogenes and cryptic loci as well as a number of genes. Finally, we demonstrate that components of the nonsense-mediated decay pathway function in at least one of the multiple, distinct WAGO surveillance pathways. These findings broaden our understanding of the biogenesis and diversity of 22G-RNA species and suggest potential novel regulatory functions for these small RNAs. 18 samples examined. Small RNA libraries generated from: C. elegans animals with mutations in the WAGO pathway and a WAGO-1 immunopercipitate.

2009-10-01 | E-GEOD-18215 | biostudies-arrayexpress

Maternal piRNAs are essential for germline development following de-novo establishment of endo-siRNAs in Caenorhabditis elegans

Project description:The Piwi-piRNA pathway represents a germline specific transposon-defense system. C. elegans Piwi, prg-1, is a non-essential gene and triggers a secondary RNAi response that depends on so-called mutator genes, endo-siRNAs (22G-RNAs) and at least one 22G-RNA-binding Argonaute protein, HRDE-1. Interestingly, through a poorly understood mechanism, silencing of PRG-1 targets can become PRG-1 independent. This state, also known as RNAe, is heritable and depends on mutator genes and HRDE-1. We studied how the transgenerational memory of RNAe and the piRNA pathway interact. We find that maternally provided PRG-1 is required for the de-novo establishment of 22G-RNA populations, especially those targeting transposons. Strikingly, attempts to re-establish 22G-RNAs in absence of both PRG-1 and RNAe memory result in severe germline proliferation defects. This is accompanied by a disturbed balance between gene-activating and -repressing 22G-RNA pathways. We propose a model in which CSR-1 prevents the loading of HRDE-1 and that both PRG-1 and HRDE-1 help to keep mutator activity focused on the proper targets.

2015-08-13 | GSE68988 | GEO

Sequential rounds of RNA-dependent RNA transcription drive endogenous small-RNA biogenesis in ERGO-1/Argonaute pathway

Project description:Argonaute (AGO) proteins interact with distinct classes of small RNAs to direct multiple regulatory outcomes. In many organisms, including plants, fungi and nematodes, cellular RNAdependent RNA polymerases (RdRPs) utilize AGO targets as templates for amplification of silencing signals. Here, we show that distinct RdRPs function sequentially to produce small RNAs that target endogenous loci in C. elegans. We show that DCR-1, the RdRP RRF-3, and the dsRNA-binding protein RDE-4, are required for the biogenesis of 26nt RNAs, termed 26GRNAs, and that 26G-RNAs engage the Piwi-clade AGO, ERGO-1. Our findings support a model in which targeting by ERGO-1 recruits a second RdRP (RRF-1 or EGO-1), which in turn transcribes 22G-RNAs that interact with worm-specific AGOs (WAGOs) to direct gene silencing. ERGO-1 targets exhibit a non-random distribution in the genome and appear to include many gene duplications, suggesting that this pathway may control over-expression resulting from gene expansion. 8 samples examined. Small RNA libraries generated from: C. elegans animals.

2010-02-25 | E-GEOD-18714 | biostudies-arrayexpress

Translation and codon usage regulate Argonaute slicer activity to trigger small RNA biogenesis

Project description:In the Caenorhabditis elegans germline, thousands of mRNAs are concomitantly expressed with antisense 22G-RNAs, which are loaded into the Argonaute CSR-1. Despite their essential functions for animal fertility and embryonic development, how CSR-1 22G-RNAs are produced remains unknown. Here, we show that CSR-1 slicer activity is primarily involved in triggering the synthesis of small RNAs on the coding sequences of germline mRNAs and post-transcriptionally regulates a fraction of targets. CSR-1-cleaved mRNAs prime the RNA-dependent RNA polymerase, EGO-1, to synthesize 22G-RNAs in phase with ribosome translation in the cytoplasm, in contrast to other 22G-RNAs mostly synthesized in germ granules. Moreover, codon optimality and efficient translation antagonize CSR-1 slicing and 22G-RNAs biogenesis. We propose that codon usage differences encoded into mRNA sequences might be a conserved strategy in eukaryotes to regulate small RNA biogenesis and Argonaute targeting

2021-04-23 | PXD020293 | Pride

High throughput sequencing of mutants in the WAGO pathway

2009-10-01 | GSE18215 | GEO

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